Could you explain the techniques for recording vocal duets? I'd like to know, for example, whether the two singers are recorded at the same time, with the same mic or with different mics, and facing each other or back to back? Also, is there any advice you can offer about polar patterns?
There are many ways to record a duet. Ideally, for a more interactive sound, both singers should be recorded together. This can be achieved with a different mic for each singer or by using a figure-of-eight pattern mic with one singer working into each lobe. The picture above shows Ibrahim Ferrer (left) and Omara Portuondo (right) duetting on 'Silencio' from the Buena Vista Social Club album. Here, they use different versions of the Neumann U87 to complement each voice.
Technical Editor Hugh Robjohns replies: This depends very much on the situation. Ideally a duet would be sung by both singers at the same time, so that they can interact and respond to each other naturally and instinctively. To do that, it helps if they are in the same room with good eye contact between them, of course. However, the wonders of technology are such that it's possible for artists to perform separately at different times and in different countries on different continents, if necessary, and then combine their efforts. Recently there have even been examples of duets recorded long after one of the artists has died!
Assuming we are talking about the two (or more) singers performing together, though, the choice of microphones would be just as normal — you would pick microphones that suited the characteristics of each singer's voice. The two mics don't have to be the same, and in the case of a male and female duet they almost certainly wouldn't be the same.
If the singers were performing in the same space, you would want to minimise spill on to each other's microphones, and that is easiest if each singer uses a cardioid pattern, with the rear null facing the other singer's mouth. You would also need to place absorbers behind each singer to prevent reflections from the other singer's voice bouncing back into the front of the opposite mic. So we have the two singers facing each other for maximum eye contact and interaction, maximum rejection from the mics, and absorbers to minimise reflections. Spacing between the singers can be whatever is comfortable, but a couple of feet would be a good starting point.
If you have two similar voices, an easier option — but one that provides less flexibility and requires on-the-spot decision making — would be to use a mic that has a figure-of-eight pattern, with one singer working into each lobe. The relative balance of the two singers is achieved by adjusting their respective distances away from the mic. If one singer is too loud, in relation to the other, they can take half a step backwards (or you can bring the other singer in slightly closer). I find the use of pop screens on separate stands useful to help control the positions of each singer.
Once you have optimised the balance, you can record the result on a single channel, but there is little scope to make changes later, so you need to be sure you can make the right decision! Usually, it's not too critical if the singers have similar voices and style, but this method won't work if one is very dynamic and the other isn't, for example.