We spoke with Bruce Bartlett, a recording engineer who writes often on the subject, and he explained the basic process of multitrack recording. Of course, the actual process will depend on the kinds of machines and equipment a particular studio has, but we'll go over a typical setup.
Bartlett says that, in the recording studio, you'll first decide which instrument or voice will be recorded onto which track. After placing the microphones near the corresponding instruments, you can then plug the different mics into a mixing console. A mixing console is a sophisticated mixer, which is a machine that combines the audio and allows an engineer to control the different volume levels of the different audio signals. An important role of the mixing console at this point is basically to amplify weak signals for the recording. But you don't have to get the levels perfect at this stage. You can tweak things to get the best sound and tonal qualities during the mix-down phase later.
The mixing console is connected to a multitrack recorder, where it sends the different microphone signals to the right track to be recorded. Some machines are recorder-mixers, which combine the two machines into one. Another option is to use a digital audio workstation (DAW), which uses a computer and software to record, edit and mix music. You can connect the instrument microphone inputs to an audio interface that connects to a computer, or use a separate mixer connected to the computer. One drawback to computers is that they're more likely to crash than recorders [source: Bartlett].
Of course, when the recording is done, it probably won't be perfect. As we mentioned earlier, one of the benefits of recording on different tracks is that one musician can make a mistake without necessarily affecting the tracks of the other musicians. If the drummer messed up a few times during the song, the engineer can rerecord the drummer's track while letting the other musicians take a break. In this situation, the drummer will be able to actually listen to the other tracks on headphones while banging away on drums, rerecording only that part of the song. The multitrack method allows this to be recorded in perfect sync with the other tracks.
But there's yet another solution. If the drummer only messed up once, that doesn't mean the entire drum track needs to be deleted.