While it’s easily possible to capture great sounds using a single microphone or a stereo pair of mics, if you read interviews with audio engineers, you know that they’ll very often use multiple microphones to record — each assigned to its own track in the DAW — then blend the tracks during mixdown to get the sound they’re looking for.
Another useful trick is to use lots of mics on, say, a guitar cabinet, even ones that aren’t necessarily where you’d usually place a mic for the primary sound. This way, you can have a lot of options for blending mics for special tonal effects, or if you want a different sound for just one section of a song. Or, using our same guitar cabinet example, you might find that while a blend of a Royer R-121 and Shure SM57 gets you “the” sound you’re looking for, combining that with a blend of a Sennheiser e609 and an Audio-Technica AT-4047 gets you a sound that blends perfectly with those two mics, and creates an immense whole. Experiment!
When you use multiple mics, the one thing you need to be aware of are the phase relationships among the microphones. Phase becomes a problem when multiple microphones record a single source, and the sound reaches each mic capsule at a slightly different time — the combination of slightly out of time mic signals results in cancellations and reinforcements that change the tonality of the recording. Use your ears to check the various combinations of microphones, listening for phasey oddities. When setting up, begin by placing all the mic capsules as close to the same distance from the source as possible. You can also correct for phase issues using a phase alignment tool, such as the Little Labs IBP.
But don’t let phase concerns slow you down. Next time you’re tracking, throw up a few extra mics for more tonal options when mixing!