Much of modern recorded music that is considered “stereo” is, for the most part, not true stero but rather panned mono (meaning that many of the individual instruments have been recorded on one track of a multitrack tape recorder and then when mixed, the instruments are panned to their appropriate positions in the relation to the left and right of the stereo spectrum). For certain instruments, it is nice to get a wide, true stereo image by setting up multiple microphones and using more than one tape track to record onto. For decades, engineers have been using many different microphone techniques with great success. The idea is anything but new, but I’d like to share one of my favorites with you.
The middle-side coincident stereo miking technique is one of the more complicated ones, but definitely worth the little bit of extra effort required. Take a bi-directional microphone and place it at a 90 degree angle in relation to the sound source (this is our side mic and will be used to pick up reflected ambient sound). Take another microphone and place it as close to the first mic as possible – without letting the two touch – and point it directly towards the sound source. This is our middle mic and can be set to uni-directional (picks up mainly direct sound), bi-directional (direct plus reflected sound from the rear) or omni-directional (a full 360 degrees of pickup range) depending on how much ambient sound you want.
In the control room, you need to use three rails of the console for this technique. Take your middle mic and pan it up the centre, equally to both speakers. Your side mic needs to be split or multied so the same signal comes up on two faders. Pan one of them to the left and one to the right, then invert the phase of either by 180 degrees. Now, you have the flexibility to mix as much of the ambient side signals with the direct middle mic as you wish.
George Kourounis, Instructor of Sound & Recording Techniques, Trebas Institute, Toronto, ON.