Chapter 4
Solo instruments
This chapter aims to cover those instruments for which there is a large body of unaccompanied classical repertoire. This includes both polyphonic instruments that provide their own harmonies (such as the guitar, harp, harpsichord, and other early keyboard instruments) and instruments that primarily produce a single line (such as violin, cello, and woodwinds). For instruments that are almost always employed as part of an ensemble, it is more practical and useful to consider how to record the whole ensemble. Therefore, discussion of brass instruments has been left to Chapters 7 and 13.
Throughout this chapter, the discussion is concerned with placement of spot microphones on a single player. It is assumed that in addition to the spot microphones, there will be some sort of overall room pickup to create a good backdrop of stereo, reverberant sound into which the spot microphones can be blended. Unless you are lucky enough to be working in an excellent acoustic environment, using two pairs will be needed to produce a sound that works well in all aspects. The overall room pair could be an ORTF-type, or omnis spaced at around 60 cm (2′), at about 2.5–3 m (8′ to 10′) high and set back by 2.5–4 m (8′ to 13′), depending on the acoustic.
When recording a solo instrument, the width of the recorded image of the instrument is a primary consideration. The sense of space and reverb around the instrument should fill the image width between the loudspeakers completely, but the width of the instrument within this should not fill the stereo picture if it is to give a realistic illusion of a live performance. A single microphone placed appropriately will be able to capture a good tonal overview of an instrument as long as it is not too close, but the result can be very one-dimensional unless there is also some sort of stereo pickup contributing significantly to the instrument’s sound. This aspect of imaging as it relates to a solo singer is discussed in Chapter 6, and the same principles can be applied to solo instruments. Even with additional stereo artificial reverb, or stereo ambient pickup microphones, a single spot microphone can dominate the mix, and the instruments’ image may become too narrowly localised, as if listening ‘down a tunnel’. Therefore, the use of two spot microphones for solo instruments is something to be seriously considered, to create a sense of width and ‘bloom’ around the image. The desired lateral image width of a solo harpsichord will be a greater than that of a classical guitar, which will be a little greater than that of a solo violin or oboe, but none of them should be expanded to fill the whole width of the stereo field or collapsed to a mono point. There is, of course, a range of image widths that will produce a great-sounding illusion of a solo instrument playing in a real space, and the final judgement is for the engineer to make. A narrow image can make the listener feel further away, even if the microphones give a sense of being closer. For the sense of distance to work, there should be no conflict between the width of the image, the close detail of the sound, and the amount of reverb.
4.1 Classical guitar and flamenco guitar
These instruments are very similar to one another, both being nylon-strung (unlike the steel-strung acoustic guitar), and the recording approach can be the same.
Guitars, lutes, and theorbos are all quiet instruments with a restricted dynamic range, so the recording venue should have a very low level of background acoustic noise, and the microphones should have low levels of self-noise. Occasionally, classical guitarists will use a small amplifier with a freestanding microphone if performing solo or a concerto in a very large venue that is better suited to orchestral music. This amplifier is not an integral part of the sound; it is there to make it louder as transparently as possible.
The sustained sound from the guitar comes primarily from the resonating front body; the string vibrations are transmitted to the body which acts as an acoustic amplifier. The sound hole is not the main source of the sound, although it is a tempting target at which to aim microphones. From the point of view of the recording engineer, the next most prominent features of guitar playing are plucking sounds from the right hand, and noises and squeaks from the fingerboard. Players always try to keep these noises from left-hand position changes to a minimum, but will vary in their ability to do so. They are usually very concerned with noises not being prominent in the recording, and you are likely to have to spend some time trying to minimise them at the time of recording (the best option) or painstakingly removing them during post production (soul-destroying, time-consuming, and therefore expensive). In flamenco playing, striking the front of the guitar (golpe) is part of the technique, and this can produce a large LF resonance from the whole body of the instrument as well as a sharp transient at the point of impact. Use of this important percussive technique will increase the overall acoustic level when compared with a purely classical guitar, and might also be used in more contemporary classical repertoire. Other player noises such as stomach rumbles can become obtrusive when amplified alongside a low level guitar signal.
4.1.1 Microphone placement and image
There is a lot of material written about pop microphone placement for acoustic guitar, but they are generally placed too close to the instrument for a classical-style solo recording. The emphasis is often on two separate spot microphones placed around 20–30 cm (8″ to 12″) away from the instrument, each capturing a certain aspect of the sound such as the main body and the fretboard. These microphones are usually too far apart to form a coherent enough stereo pair, and so they form two pools of mono signal that are combined to create an overall tonal representation of the instrument, if not a good spatial impression. They may be panned almost to the same place, but the aim in a pop song is not to create the sense of a guitar playing in a real space but to capture the closer sound of the instrument that can be placed into a mix.
For classical guitar, a simple narrowly spaced stereo pair can be placed at about the height of the centre of the guitar, perpendicular to its front surface. If the guitar is angled upwards slightly when played, move the microphones higher to look down a little. Fine tuning the placement of the microphones can be helped by sitting on the floor with your head at microphone height, and moving around the instrument to see how the sound changes. As a starting position, aim the left microphone at the bottom of the body and the right microphone at the bottom of the fretboard. This will place the fret noise a little to the right, but this seems to work acceptably when listening to a guitar recording. Lateral movement around an arc will help to reduce or increase the noise from the fretboard if it is too intrusive. (See Figure 4.1.)
The pair should be spaced around 25 cm (10″), pointing forwards at a distance of 70–100 cm (2′4″ to 3′4″) from the guitar (if the room is a nice sounding one, a little closer if not) with a suitable amount of natural, smooth reverb. The image width that works best for classical guitar is to fill around 30% of the total stereo field. If it were too wide, it would give the listener an unreal sense of the instrument’s size, and the creation of a real sense of perspective and space would not be successful. A guitar would only fill the listener’s field of view if they were seated about 30 cm (1′) away, but the microphone placement and amount of reverb used give cues to the listener that place the player further back than this.
Finding an appropriate balance between the reverberant and direct sound by altering the distance at which the microphones are placed can be difficult to get right with classical guitar. There is a conflict between trying to pick up this quiet instrument in a reverberant environment by moving in closer, and avoiding the close microphone placement that produces intrusive fret noise or a very localised tone quality. If you have problematic fret noise, move the microphones to at least 1 m (3′4″) away, and adjust their position around the arc by ear (see Figure 4.1). If you find that omnidirectional microphones at this distance are now picking up too much reverb, switch to directional microphones. This will cut out some of the reverb and give you a dryer but not too close sound to work with. Ribbon microphones (Royer R-121 or Coles 4038) in particular can be useful because their HF roll-off will soften fret noise, and an additional, more ambient pair of omnis can be used as a room pair to collect some reverb and warmth of tone.
Figure 4.1a Classical guitar microphones – plan view showing line of lateral adjustment
A room with a high level of background noise will present similar, related difficulties. Microphones need to be close to record sufficient level from the instrument over the background noise, but this means that you might struggle with prominent finger squeaks and lack of reverb. Additional room microphones will be needed for the room reverb, and using ribbon microphones might help with the squeaks.
If you have to record a guitar, lute or theorbo in an orchestral or large ensemble context, you will need to be closer to pick up sufficient level and detail. This will of course be in addition to an overall orchestral pickup, so will be primarily used to make sure the transient details are not lost, and some contact with the finger noise is actually desirable to help the instrument be heard. A distance in the order of 15–25 cm (6″ to 10″) would be recommended, but you will need to beware of the possibility of proximity effect (an increase in the low frequency components) on any directional microphones at this distance, and correct for any excessive LF colouration if it is audible once mixed with the orchestra. If you have to use a single microphone in this context, start with it about halfway along the total length of the guitar (neck and body combined) and move it laterally until the balance between fretboard and main body of the sound is satisfactory. (See also Chapter 11 for concerto recording.)
4.1.2 Using artificial reverb on guitar
If the space in which you are recording is a dead room, or has poor sounding reverb, then artificial reverb can be added afterwards instead. However, artificial reverb can inadvertently emphasise finger noise that was relatively unobtrusive when it was recorded dry. A squeak is much more troublesome to the listener if it has 2–3 seconds of bright sounding reverb tail attached. In a real space, the HF content of the squeaks does not travel too far into the room because high frequencies are partly absorbed by the air. Hence, the ratio of ‘squeak to music’ picked up by the microphones gets higher the closer to the instrument the microphones are. The squeaks are not as present in the real room reverb as the other parts of the sound because they are at a reduced level by the time they reach a room boundary for reflection. If you are adding artificial reverb, this is something that you can try and control as part of setting the parameters. If you are using a programme that does not enable you to control the HF behaviour of the reverb algorithm in a sophisticated way, you can use a gentle HF roll-off on the auxiliary send that you are using to drive the reverb, and a similar roll-off on the reverb returns. Adding a small amount of EQ to both send and return will often give better results than EQ’ing only one of them more drastically.
4.1.3 Microphone choice
The lowest note on the classical guitar is E2 at approximately 82 Hz, and so some good cardioids (e.g. Neumann KM84) will adequately cover the frequency range without the loss of any fundamental frequencies. Omnis (such as the KM83) might be preferred for the main guitar microphones if the location is good, and a natural balance between the room and the instrument can be found. Because they have a more extended bass end, you are likely to find that they will pick up some lower resonances from the body, but the preference for the sound is a personal one; the use of directional microphones should not affect important frequency content unless they have a roll-off that affects the 50–100 Hz range. As noted earlier, ribbon microphones will work very well, and they have the advantage that the HF roll-off will reduce the prominence of any fret noises and squeaks which can be particularly useful if you have to get in a bit closer. With fig of 8 ribbon microphones in particular, you should be aware of the possibility of the proximity effect starting to cause some artificial bass colouration if you are closer than 60 cm (2′) or so. This can be attractive in small amounts, but LF is seductive; you should be careful of being seduced by a sound that is large, warm and boomy but not actually like a classical guitar. As discussed earlier, using omnidirectional microphones for an ambient room pair, and ribbon microphones or cardioids for a more detailed pickup of the guitar can be a very successful combination. Avoid microphones that have any sort of HF lift above about 7 kHz that can make the instrument sound thin. If electrical noise (hiss) is proving a problem and you have optimised the rest of your signal path and gain structures, it is worth remembering that large diaphragm condenser microphones have a lower self-noise and higher sensitivity than those with small diaphragms, so require less mic gain.
4.1.4 Floor and surfaces
Floor reflections from a wooden floor can really enhance the sound of a classical guitar. Stone floors are too bright and immediate, as are some types of modern varnish on a wooden floor. If you have to record in a carpeted space, try placing some sheets of wood, plywood or medium-density fibreboard (MDF) under the player’s chair to improve the sound of the instrument.
4.2 Harp
The orchestral concert harp has a wide dynamic range, and it is a large and powerful instrument when compared with its folk music cousins. Its sound consists of a distinctive plucked transient followed by a sustained resonating tone that comes both from the strings and the soundboard (although this is more of a resonator like a guitar body than a soundboard like that of a piano.) The range of its strings’ fundamental frequencies extends from C1 at approximately 32 Hz to G7 at 3.1 kHz, so it approaches the piano in terms of its range once overtones are included. Therefore, in order to pick up the full effect of the lower frequencies in a solo recording, using omnidirectional microphones to form at least part of the sound is to be recommended.
The concert harp also has pedals which are manipulated to raise and lower the pitch of a given set of strings, creating the ability to play sharps and flats as required, and making the instrument chromatic in nature. These pedals will make some noise when they are being engaged or disengaged, but as long as they are not too obtrusive in the recording, they can be considered as part of the instrument’s natural sound in the same way as woodwind key noise and guitar fretboard sounds. The opinions of engineers, producers, and performers concerning how much instrumental noise is tolerable can vary widely; it is unrealistic to try to eliminate these sources of noise completely, and accepting them as part of a real human performance on a real instrument will avoid the recording being processed into a state of unnatural and clinical quietness.
4.2.1 Solo harp image
The temptation when recording a solo harp might be to create an over-wide, rather ‘technicolour’ harp so that a full glissando travels from one loudspeaker and into the other. While this might have been fun in the early days of stereo and film scoring, or if used as a magical sound effect, we are trying to create the illusion of the sound of a real instrument in a real space, and therefore we need to constrain the image to something more central. In accordance with the techniques outlined for soloists so far, a forward facing pair spaced at 25–30 cm (10″ to 12″) apart can be used to create an image of the harp that is not overwide even when fully panned, although angling the microphones apart a little will increase the image width if this is desired. Spacing the microphone more widely will result in two less correlated sources, one picking up lower strings, and one higher. This will create some dramatically wide glissandi when panned left and right, but little sense of a real instrument or a real space. (See Chapter 9 for dealing with the harp in an orchestral context.)
4.2.2 Microphone position and choice
The player sits with the harp resting on their right shoulder with the soundboard close to their body. The player can then look along the rows of vertical strings, with the highest notes nearest to their right ear and right hand. This allows the player to reach forward with the left hand to the lower strings, and to have a clear view of the music stand which is placed on the left-hand side of the instrument (from the player’s perspective).
Figure 4.2a and 4.2b show the harpist and some microphones positions to be discussed below. Positions A and B are useful; position C is to be avoided.
Figure 4.2b Harp – end view showing height for positions A and B
The microphones for positions A and B are placed sideways on to the instrument, aimed at a position midway down the strings from a height of around 150–180 cm (5′ to 6′) and about 90–120 cm (3′ to 4′) from the harp. In position A, the microphones are on the player’s right-hand side, and this can be preferable to position B, as the finger noise is a little reduced from this side. In all other respects, position B will also work well, as long as the microphones can be placed to look above the music stand. Omnidirectional microphones would be the preferred choice if the room is sufficiently nice sounding, because of the extended frequency range of the instrument. The distance of 90–120 cm (3′ to 4′) from the harp will be close enough to get some good detail and pick up the quietest passages from the top strings, but not so close that the sound becomes localised to one part of the instrument.
If the engineer concentrates on the soundboard as the source of all the sound and moves the microphones around in a 90° arc to look straight at the soundboard from the front end of the harp (position C), odd phase relationships and cancellations can result. A more extreme version of this approach is to put one microphone on either side of the harp; this will result in two rather uncorrelated microphone signals which will not create a convincingly located instrument in the recording image. As noted at the start of the chapter, an overall room pair should be added to complete the sound.
4.2.3 Floor and surfaces and noises
As with the guitar, a nice wooden floor will enhance the resonance and sound of the harp. However, the pedals will create some noise acoustically and also have the potential for transmitting noise mechanically through a sprung floor. The best way to ameliorate this is to use some good isolation mounts for the microphones to avoid pedal noise transmitting itself in this way. If you are still picking up too much pedal noise, have a listen in the room with the player and see if this is how the instrument sounds anyway. If it is noisy in real life, talk to the player about it to see if anything can be done. If it cannot be improved by the player adjusting the instrument, it can be worth adding a small piece of carpet under the pedals as you might for piano, where the back of the player’s heel is on the floor. Avoid using a large rug as it will be better for the overall sound for most of the interaction with a wooden floor to be included. Remember that some pedal noise is fine as it is part of the instrument; along with finger noise, it is only a problem if it starts to sound very close and out of context with the rest of the sound. This arises because we usually place microphones closer than we would sit to a performer in a concert, and if misjudged, this can lead to instrumental noises becoming too obtrusive.
4.3 Violin
The violin (along with the guitar and orchestral stringed instruments) consists of resonating strings that are coupled to a body that acts as an acoustic amplifier. The body produces the majority of the sound from its own vibrations and that of the air inside it. It has a very extended frequency spectrum containing high levels of HF overtones that give the instrument its character. Both the higher frequencies (for the sense of contact and connection with the instrument) and the lower frequencies (for a feeling of warmth and resonance) are needed for a beautiful and well-balanced solo violin sound.
The radiation pattern is complex, but taken as a simplified overview, the lowest frequencies are radiated more or less omnidirectionally, and the higher frequencies are beamed upwards perpendicularly to the front face of the body.1 The higher the frequency, the narrower the beam of radiation. Consequently, placing microphones above the player will capture all the frequencies produced but may not be very flattering if the player is less skilful or harsh in tone. In a concert situation in an appropriate environment, the room will integrate the whole sound before it reaches the listener, in a similar way as happens with a classical voice. When recording a live concert, the choice of where to put microphones is restricted because of the resulting visual intrusion; thus microphones are often placed much lower down, and hence they do not capture the upper overtones. The engineer is then reliant on capturing some of this HF on other microphones within the room, usually on some sort of overall pickup placed higher and further back.
4.3.1 Microphone placement
Violinists are like singers in that they will move around quite a significant amount during a performance, and any microphone technique needs to be able to manage this situation adequately, without the image moving in and out of focus or from side to side. The majority of soloists will perform standing up, so all distances given in this section are in relation to a standing player of middling adult height, perhaps 1.7 m (5′7″). If the player is seated, you will need to lower the microphones accordingly.
With a professional player with a good tone, a reasonable starting point would be to place a pair of microphones about 90–100 cm (3′ to 3′4″) back from the player, looking down at the instrument from a height of 2.4–2.85 m (8′ to 9′6″) (see Figure 4.3a and 4.3b). This should produce a well-balanced overview of the whole sound, the aim being to achieve a good balance between a sense of space around the instrument and giving the listener a feeling of immediate emotional contact with the player. The balance between contact and spaciousness can be altered with the height of the pair, and it must be judged in a given context; the height that works will depend on how reverberant the room is and the directivity pattern of the microphones. The distance between the microphones and the violin also serves other purposes; it will reduce any uncomfortable closeness and intrusive bowing noise by means of the loss of HF with distance, and it will reduce the impact of player’s movements on both the tonality of the sound and the stability of the image. Microphones placed lower down in front of the player at around the instrument’s height of perhaps 1.5 m (4′11″) will lose the ‘presence’ of the bowing and HF components, and will need to be further back than 1 m (3′4″) to recover an appropriate balance between direct and reverberant sound within the room. Overall, it is harder to achieve a really pleasing balance between spaciousness and detail with the microphones placed lower down.
Player movement is something that can cause problems, particularly when using a pair of spot microphones. Initially, the microphone pair should be 25–30 cm (10–12″) apart, parallel to one another, and panned fully left and right to produce a central image with some ‘bloom’ around it. If the image swings around a lot when the player moves, these can be panned in up to around 75% (following the same principles outlined in Chapter 6) to reduce image instability. If this isn’t sufficient to tame the movement, you can reduce the spacing of the pair to the lowest end of the suggested range, and physically angle them inwards slightly. Another technique that works extremely well is to add a central ribbon microphone (Royer R-121 or Coles 4038) to the violin pair and use this at a lower level in the mix to stabilise the image, as discussed in section 4.3.2.
Figure 4.3 shows a good starting position for placing the close pair on a violin.
The most common problem will be too bright a tone, or too harsh a tone with a less good player; this can be reduced by changing the microphones’ horizontal angle and pointing them a little over and beyond the instrument (Figure 4.4a). This will move the instrument away from the front axes of the microphones and thus reduce the HF content. If this is not sufficient, you could reduce the height of the microphones in order to move them out of the way of the highest frequency projection that is perpendicular to the instrument’s bridge and front face (Figure 4.4b). However, the microphone height does give a good feeling of space, and it can help avoid floor reflections, so rather than sacrificing height, you can also try moving the microphones around in an arc as shown in Figure 4.4c. The further around towards the left (on the diagram) that you go, the more the HF will be reduced as it will be effectively blocked by the player’s head. Microphones behind the player might be useful in a concert scenario; however, they will also result in a loss of HF as the player holds the instrument to project forwards and upwards – not behind him or her. The best choice of technique for altering the HF content might depend on how the player characteristically moves; spend some time watching them play and observe where they tend to move and how much they move. This should enable you to get a good microphone position according to their ‘average’ playing position. If movement is extreme, microphone placement off-axis from the instrument’s bridge will reduce the degree of HF change that occurs as the instrument swings around. (Figure 4.4a through 4.4c show different ways to alter the amount of HF on a violin.)
As before, an overall room pair should be added to complete the sound.
4.3.2 Microphone choice
The lowest fundamental frequency of the violin is G3, at 196 Hz, and so a good quality condenser cardioid or omnidirectional microphone will be sufficient to pick up the lower end and warmth of the tone. As with all acoustic recording in a live space, the off-axis response is important when collecting room reverb, but in the case of a solo performer, other off-axis instruments do not need to be considered. Cardioids will pick up less of the room reverb at the suggested height and would be a good choice in a very live space. They will enable you to remain at a comfortable distance from the instrument while keeping the amount of reverb under control.
Figure 4.4a Change microphone angle to look over the instrument
In addition to the suggestions in Figure 4.4 for reducing the amount of extreme HF picked up, ribbon microphones can also be considered, either for the pair or as an additional central microphone (see Figure 4.5). The smooth and gentle HF roll-off will ameliorate any harshness in the tone but will still pick up some room reverb on the rear lobe. A useful technique for a recording session, as previously noted, is to combine a pair of condenser microphones mounted a little higher, at around 3 m (10′) (this increased height will reduce the amount of HF slightly as it is absorbed by the air), and a single ribbon microphone mounted about 30 cm (1′) lower.
The ribbon can be placed closer to the violin because of its HF roll-off, and this might be a useful asset where being closer is necessary, perhaps because of the acoustic or some other constraint on microphone placement. This combination of a pair of condensers plus a central ribbon microphone allows you to use the ribbon microphone to fix the image more securely in the centre if it exhibits a lot of lateral movement on the condenser pair when the player swings around. The ribbon microphone will usually be mixed in at about 6–8 dB lower than the condensers, so it plays a secondary role in forming the sound, but it can be used to have a beneficial effect on the tonality as well as on the image stability. It will give a warmth and sweetness to the tone, while the condensers pick up more of the attack, bowing noise, and other HF components. The violinist Itzhak Perlman particularly likes ribbon microphones such as the RCA 44BX, and Coles 4038s were used while recording him in 1998 at the Saratoga Performing Arts Centre in New York during his collaboration with the pianist Martha Argerich.2
4.4 Cello
The cello radiates from its body in a similar way to the violin, in that the very highest frequencies are radiated perpendicular to the front surface and the bridge, and the overall pattern is quite complex. However, in comparison to the violin, it has been found that microphone placement is a little less critical, and moving on- and off-axis from the bridge will affect only the highest HF content. Its lowest fundamental is C3 at 130 Hz, which suggests that a good cardioid will extend low enough in the frequency range, although an omni might give a better tone.
Figure 4.5 High condenser pair plus a ribbon microphone on a violin
The instrument’s playing position is very different to that of a violin in that it rests on and is close to the floor. The reflections from the floor are important to the sound, and so a solid wooden surface would be the preferred choice when making a recording. A marble or stone floor is not flattering because of its bright reflections, so if you have to record using such a floor in a church for example, then put a small amount of carpet down underneath the player’s chair. Carpet will absorb HF, so bear this in mind when choosing to use it in other circumstances, and avoid using a large area of it.
Some solo players like to sit on a podium to play because it can act as a further resonator and enhance the sound, but a podium’s performance will depend on how well it is constructed. Some will enhance the sound, but others will absorb some of the LF, or produce an unpleasant resonance, or simply be creaky and noisy as the player moves. If the podium is working against you, you will have to negotiate with the player to find another solution.
4.4.1 Microphone placement and choice
The technique outline for the violin can be adapted for the cello, using a narrowly spaced pair of microphones (25–30 cm (10″ to 12″)) to give the solo image more substance and width, and aiming to capture a good balance of bowing detail, full tone, and sense of space. Because the playing position is different to the violin, the microphones do not need to be as high to capture the HF, but they can be placed in the region of 2.25 m (7′6″) high and 1.8–2.1 m (6′ to 7′) away, depending on the room acoustic and the microphones used. The microphones should be pointed towards the bridge, perpendicular to the instrument’s front surface, and as you move the microphones around in an arc L to R, you will find that the HF is maximised when they are centrally placed in front of the instrument. Figure 4.6 illustrates the microphone position suggested as a starting point. In order to get a good feeling of a real instrument in a real space, moving the microphones a little closer or further away will help adjust the balance between direct and indirect sound.
In a concert scenario, any microphone will have to be placed lower, but this is less critical than it would be for the violin; there is a wider acceptable range because the instrument is less directional in its radiation when floor reflections are taken into account, and it is orientated differently with respect to the microphone. A microphone low enough to be looking straight at the bridge will be visually unobtrusive for live work, and a fig of 8 ribbon (Royer R-121 or Coles 4038) could be used to usefully discriminate against the orchestra.
Condenser omnis or cardioids will work well, remembering that it is not necessary to have a large-diaphragm microphone in order to capture a good extended LF range. Any pencil omnidirectional microphone will have a sufficiently extended frequency response.
The cello is also well suited to ribbon microphones using the HF roll-off to produce a mellow sound, and it enables closer placement if necessary. At the microphone distances suggested earlier, the proximity effect from the ribbon microphone should not be at all evident, but it will begin to show at the lowest frequencies at around 0.7–1 m (2′ to 3′4″) away – more likely in a difficult live scenario. As with the guitar (which has a similar frequency range), care should be taken not to make the instrument sound unnaturally bass heavy and larger than life. Its tone needs both the warmth and the more astringent upper frequencies to feel well balanced and real. Although the ribbon microphones will miss some of the upper HF that would add some bite, this part of the tone colour will be picked up on the overall room pair of condensers.
Figure 4.6a Microphone placement on cello – plan view showing arc for HF adjustment
4.5 Woodwinds
In radiation terms, the woodwinds can be divided into the oboe, clarinet, and bassoon, which all have reeds and are essentially closed at the mouthpiece end and open at the bell; and the flute, which operates using a stream of air striking the mouthpiece edge, and is open to the air at both the mouthpiece and far end. This has an impact on the radiation patterns, and thus which microphone placement options are most effective when recording them.
4.5.1 Oboe, clarinet, and bassoon
For the first group of instruments, radiation comes from both the open holes and the bell. The highest overtones pass right down the bore of the instrument, radiating partly from the open tone holes but primarily from the bell, forming a cone-shaped beam aligned with the axis of the instrument. At the lower end of the frequency range (i.e. the fundamental frequencies of the lower register), the radiation becomes stronger from the first open holes than from the bell, and the overall radiation pattern becomes more perpendicular to the instrument’s axis.3 The higher frequencies emerging from the bell will be reflected from the floor (for the oboe and clarinet whose bells point in that direction) and projected diagonally upwards from the bassoon. The techniques used for the violin can be adapted for the forward-facing woodwinds, although HF content will be best adjusted with microphone height and angling rather than moving side to side as there is no head-shadowing. You should avoid placing microphones directly on-axis to the bell of the woodwind instruments, as you will collect more HF and wind noise and miss out on obtaining a good overall balanced tone, which is the goal of classical recording.
Microphones should be positioned in front of the player, but at a height of around 2.25–2.6 m (7′6″ to 8′6″) and looking down (assuming the player is standing; a bassoonist might prefer to sit and the microphones can be lowered accordingly). Height is less critical for the clarinet and oboe than it is for the violin because of the different radiation characteristics of the instruments in conjunction with the floor reflections of the bell radiation, although key noise needs to be avoided. As outlined previously, to obtain an image that has some width and bloom around it, a pair of microphones instead of a single spot microphone is used.
Figure 4.7 Generic end-blown woodwind radiation pattern at low, mid, and high frequencies. This applies to overtones as well as fundamental frequencies.
Key noise is the aspect of woodwind recording that will cause the most difficulty, although bubbling and wheezing noises from worn or leaky reeds can also be a nuisance, and it would be best to politely talk to the player and see if they can change their reed where this sort of noise becomes intrusive. Key noise is part of the instrumental sound, so it has to be accepted to a certain extent, but it should not dominate. Keeping the microphones at a good distance (above about 2.25 m (7′6″)) will help with this, as the intrusiveness of transient-filled key noise is reduced by HF absorption into the air. If the microphones are too close, all key noise, reed noise, and mechanical sounds will be artificially exaggerated and feel very unnatural to the listener, who does not usually hear the players close up. If the room is reverberant, it will be better to avoid getting in too close (and picking up too much key noise) by using directional microphones rather than omnis. Ribbon microphones (Royer R-121 or Coles 4038) will also ameliorate key noise by virtue of the HF roll-off inherent in the design.
4.5.2 Flute
The flute can be placed in a different category of radiation pattern because it is supported more or less horizontally in its playing position, and its radiation comes from both ends of the instrument as well as any open holes.4 The result is that it radiates almost equally to the front and to the back of the player, which can be very useful in opening up microphone placement opportunities in less than ideal circumstances. Placing microphones fairly close and halfway down its length should be avoided, as some phase cancellations may result due to some frequencies radiating in opposite phase from each end. The breath noise is more prominent from the front, as it is formed by air turbulence as the breath strikes the top of the mouthpiece. If too much breath noise is a problem, make sure the microphones are not in front of the player or at the height of the player’s mouth; because of the equal front and rear radiation, you will be able to move the microphones behind the player to really reduce breath noise. Key noise, as with all the winds, will be reduced with distance, so if you are working in a reverberant space, keep the microphones at least a couple of metres (6′8″) away from the instrument, but use cardioids instead of omnis to reject a greater proportion of indirect sound.
Figure 4.8 Woodwind player with microphones – side view
Adding microphones from behind at approximately instrument height is a good, discreet option in a live situation, and unlike for the violin, this will not result in the loss of important HF content.
Figure 4.9 Flute – alternative microphone positions in front and behind
4.6 Harpsichord
Although the harpsichord is clearly an early relation of the grand piano, the technique of piano recording outlined in Chapter 5 cannot be simply transferred over to the harpsichord; its radiation pattern is different, and obtaining a balanced and characteristic sound needs a slightly different approach.
4.6.1 Harpsichord characteristics
The instrument is not as loud as a modern piano; the string tensions are lower, the soundboard technology is not as developed, and gradual changes in dynamics are not possible as the instrument’s mechanism is not responsive to the velocity with which the keys are struck. To facilitate stepped changes in tone and dynamics, harpsichords have stops in a similar way to organs, which are a means of coupling together sets of strings in a variety of different octaves. Engaging and disengaging these will produce a significant amount of noise, as the mechanisms are relatively simple and primitive in design. The pedals can also make quite a lot of noise; placing a small piece of carpet on the floor under the pedals can reduce this.
The largest instruments have a range of five octaves, from F1 at around 40 Hz to F6 at around 1400 Hz. The exact pitch is dependent on the tuning being used; they are usually tuned to a lower pitch than A = 440 Hz, as would be normal for instruments of the baroque era, whether they are original instruments or reproductions. The upper frequency limit of the whole spectrum is much higher than 1400 Hz because of the strong presence of a multitude of higher partials. In order to fully capture the lower notes, omnidirectional microphones would be preferred.
4.6.2 Microphone placement
The majority of the harpsichord’s useful sound is projected out to the side away from the lid and towards the audience, and the effect of the lid reflections is to add a layer of complexity and richness to the sound. When recording the piano, the practice of approaching it from the tail end is in part an attempt to reduce some of the complications that arise from the muddying effects of the lid reflections. With the harpsichord, these same lid reflections can be very useful in helping to integrate the sound and effectively glue it all together. Increasing the lid’s angle so it is open more widely will affect the openness of the sound, and this is something you should experiment with. It is possible to remove the lid altogether, but the effect will be to lose some of the characteristic complexity.
If microphones are placed around the tail end, the mid and lower string resonances will be picked up, but not so much of the strong upper harmonic components of the strings and the characteristic plucking sound of the mechanism. All three are important aspects of the overall sound that needs to be captured to give a balanced view of the instrument.
Figure 4.10 shows the harpsichord from above and the side, showing the most useful arc in which microphones should be placed.
Given the lower overall level of output, it is usual to place the microphones somewhat closer than for a grand piano, and a good place to start will be in the region of 1.1–1.4 m (3′6″ to 4′6″) away from the well of the instrument at a height of about 1.5–1.65 m (5′ to 5′6″).
Increasing the distance of the microphones away from the instrument will reduce clarity and increase the amount of reverberation, but it will also reduce the amount of mechanism noise, which is potentially useful. However, the amount of mechanism noise can also be altered by the height of the microphones without the need to move them further away if this has a detrimental effect on the clarity of the sound. When the instrument lid is fully open, a lower microphone position will pick up more of the plucking, and a higher one will have more resonance and sustain. Microphone height adjustment will also affect the amount and quality of lid reflections collected, so it is worth spending some time altering this aspect of the placement to find the best place on any given harpsichord. This is also a good time to take a walk around the instrument and sit at different heights to give yourself an idea of just how much the sound changes.
The overall aim is to find a happy medium where there is enough clarity (so the recording is not dominated by room sound) whilst also ensuring that the mechanism sounds are not unduly intrusive. Making sure that the sustained part of the tone is well captured across the whole spectrum will help to make listening to the recording really enjoyable. Listening to a harpsichord recording where the transients are very harshly represented can become fatiguing.
The microphones used in Figure 4.10 are a spaced pair at around 25–30 cm (10″ to 12″), angled slightly outwards, in addition to an overall room pair. The LCR three-microphone technique outlined in section 5.7.1 can also be used on harpsichord, although they will be closer together as the physical size of the instrument is not so great. Because of this, they could be panned almost fully LCR, but the final width of the image should inform the panning. In order to make the image and sense of space feel real, this technique will need more support from some sort of overall room pickup to act as a unifying element.