Many beginning home recordists get confused between recording to a mono or a stereo audio track. Isn’t stereo better and wider? So why record to a mono track? What usually happens is they try to record to a stereo track, but find that their vocal is only playing through one speaker. If the DAW lets them, they fix this by setting both left and right inputs to the same source. Now they are recording the exact same information to left and right of a stereo audio track. Better? Thicker? Fuller? Not at all.
It’s About Panning
There is no difference between a mono track panned to the middle and a stereo track with identical information for left and right. The thing that beginners miss is that both mono and stereo tracks in a DAW usually have stereo outputs. Mono or stereo is referring to the source, not the output. A mono track panned in the center is sent equally to the left and right output to create the effect of sounding in the middle of the speakers (phantom center). When the panner moves to the left, more signal is sent to the left speaker and less to the right to make the image shift to the left. Click here to learn more about how panning works. A stereo track has two sources that are usually slightly different than each other. These differences create a stereo image. If the signals are identical, you’re back to the mono signal in the center.
The simplest rule to follow is if you are recording one microphone or one guitar input, you will record to a mono track (which you can later pan left or right). If there are two microphones on a source or two outputs of a keyboard or two outputs of a pedal or guitar processor, you will record to a stereo track.
Making Mono Stereo
Now if you want to get tricky and make a mono track have a stereo sound or effect it’s all about duplicating the sound and making one different than the original in some way. There are lots of ways to do this. The simplest is to delay the duplicated track. This can be done with a delay plug-in or by simply moving the audio later in the timeline. A delay that is less than 50 miliseconds (50 thousandths of a second) is going to sound like a thickening of the sound. A delay that is more than 50 miliseconds (50 thousandths of a second) is going to sound like an audible repeat. A stereo chorus uses this technique, but also varies the pitch of the delayed signal to make it sound like a choir (where two voices are never always hitting the exact same pitches). Adding a bit of EQ or compression won’t necessarily do the trick, but could create an interesting stereo effect.
It is incredibly popular in many genres of music today to stack parts like vocals or guitars. Many novices try to take short cuts by duplicating tracks as mentioned earlier. This may work (with some tweaking), but nothing can replace the thick sound created from a great vocalist recording four different takes of the same part, or the wall of sound created by multiple distorted electric guitars. Stacking can be done on anything from bass to vocals to shakers. The key is consistency. If the parts are not played the same, it will just sound like a jumbled mess. Most professional examples of this technique are tightened up in the editing process with melodyne, vocalign or elastic audio. This allows the engineer to match up slight timing variations from multiple takes. This doesn’t mess up the stereo effect because the takes will always be slightly different (even with heavy auto-tuning).
There are no shortcuts in making mono stereo. Either you record with two mics or sources, you record a mono signal and duplicate it and delay or process the duplicate, or you record at least two close to identical takes of the mono source panning them left and right.