There seem to be instances where several mics are used to record an instrument, such as a guitar amp or drum kit, but I've never heard of this approach with vocals. Is there a reason for this? Does anyone have any experience of recording vocals with multiple mics at different distances from the singer?
SOS Forum Post
SOS contributor Mike Senior replies: There is one good reason why vocals aren't often recorded with multiple close mics, when guitar amps and drums kits regularly are: most singers move around a little (or a lot!) while they sing. These movements can change the relative distances between the singer and each of the microphones. If the microphones are both fairly close to the singer, it effectively means that you get two very similar recorded waveforms which keep shifting very slightly out of alignment with each other, resulting in a kind of subtle phasing effect.
If you get the mics close enough to each other you can restrict the effects of the phasing to the extreme high frequencies, but this can still pose a problem, given that high frequencies are usually so important to expensive-sounding recorded vocal sounds. It's not something you can easily correct by shifting the waveforms around in your sequencer, either, as the alignment of the recorded waveforms will constantly change as the performer moves.
That said, there are some famous recorded examples of vocals recorded with two fairly close mics combined. For example, John Hudson talked about recording Gary Glitter and Tina Turner using two close mics back in SOS May 2004 (www.soundonsound.com/techniques/classic-tracks-tina-turner), although he made it clear that he used the technique primarily to gain extra control over their extremely wide performance dynamics.
Supplementing a single close mic with an ambient mic or two, however, offers a bit more potential. If the ambient mic is at least a couple of metres away, its recorded waveform will be different enough from that of the close mic that the phasing effects will tend to be much less noticeable; it will pick up a much more complex signal combining the direct vocal sound with reflected sound from the room.
Probably the best-documented example of a recording where ambient vocal mics were used is David Bowie's 'Heroes', which Tony Visconti discussed in the SOS October 2004 Classic Tracks feature. A heavily compressed Neumann U47 close mic was joined by Neumann U87s further away, the latter being gated in such a way that they only opened to give a more reverberant sound when Bowie sang loud. Michael Stavrou also talks about using this kind of technique in his book 'Mixing With Your Mind', although he suggests controlling the levels of the ambient mics with mixer automation, which allows for a bit more precision at mixdown.
Jack Douglas, engineer for many of Aerosmith's most successful albums, has also mentioned that he often combined close and ambient mics for Steven Tyler's vocals. Unusually, though, he used a Shure SM57 dynamic up close and a heavily compressed Sennheiser shotgun mic about five feet away. The SM57 not only captured part of the final sound, but was also useful for giving Tyler something to focus on, keeping his position fairly consistent relative to the shotgun mic. For similar reasons, some engineers who only record a single vocal mic will still use a second mic as a prop to keep the vocalist rooted in the main mic's sweet spot, particularly where no pop shield is being used.