Fig. 1a (top). Here’s a downbeat on which the bass (the purple stereo track in the middle) is hitting late, and the rhythm guitar (red track on top) is a tad early.
Fig. 1b (bottom). The guitar and bass have been corrected here (notice that they have crossfades at their boundaries), so that they line up with the kick (bottom track, in blue).
Correcting rhythm and pitch has become a routine element of music production. There are plenty of pitch-correction applications on the market (Antares Auto-Tune and Celemony Melodyne, among others), and many DAWs offer built-in tools for correcting pitch, rhythm, or both. (For example, MOTU Digital Performer has Audio Pitch Correction and Beat Detection Engine, Cakewalk Sonar X1 has V-Vocal for pitch and Audio Snap for rhythms, and Pro Tools has Elastic Audio and Beat Detective.)
Even with these tools available, there are times when it’s easier just to perform a quick manual correction using basic editing features or standard pitch-change plug-ins, instead of breaking out the heavy artillery, no matter which DAW you use. And if your DAW doesn’t have built-in correction, the manual methods I’m about to outline can be even more useful.
Beat Not Neat Let’s start in the realm of rhythm. If you want to quantize a song’s entire multitrack drum part, you’ll need a dedicated feature such as Pro Tools’ Beat Detective or Elastic Audio, Digital Performer’s Beat-Detection Engine, or Logic’s time-stretching feature. But in a situation where there are a just few spots where some of the musicians were not locked in rhythmically, you can make corrections quickly and easily with basic editing techniques.
Most pop, rock, or country songs have numerous beats on which the kick, bass, and rhythm guitars are all supposed to hit together. But when dealing with live musicians, there will often be two or three instances in a take in which the players land on the beat far enough apart that the effect is noticeable (see Figure 1a).
First, put the tracks that need correction next to each other in your DAW window that displays track lanes. Enlarge the lanes vertically, and zoom in horizontally on the waveform until you can clearly see the beginning of the beat in question. In many DAWs, if you place the cursor at a specific spot, or make a selection starting at that spot, you get a vertical line that goes across all the track lanes. You can use this as a reference point if you click it at the point in the timeline where you want all the musicians to hit. If you don’t have this feature, just eyeball it, using an instrument that landed on the beat correctly as your reference point. If you played to a click, you could also use the beat on the DAW’s grid as your reference.
Going one track at a time, select the beginning and end of the note or chord that hits in the wrong spot, separate it, and then drag or nudge it closer to the correct spot. As long as you’re zoomed in enough, eyeballing should work fine. If you can extend the borders of the neighboring notes cleanly, do that, then crossfade around the boundaries of the note you separated and moved (see Figure 1b).
Be careful: The act of separating and moving a note or chord can cause it to sound unnatural—either before or after the separation. Crossfading at the boundaries makes transitions sound better; if there isn’t enough clear audio to crossfade, try putting a short fade at the beginning or end of the note you’re moving. Even if the new transition sounds odd when it is soloed, it often gets covered up once you put the other instruments back in. So make sure to audition the edit in the mix before deciding that it didn’t work.
Relief Pitcher Let’s talk about pitch. If you have just a couple of out-of-tune notes in a track, you might not want to treat the entire track with a pitch-correction plug-in, which can affect the overall timbre. If your DAW doesn’t have a feature that lets you easily quantize the pitch of selected notes, and there are only a few problem spots, consider using your good old destructive pitch-shifting plug-in (such as AudioSuite in Pro Tools, or the rendered plug-ins in DP; see Figure 2).
| Fig. 2.
The out-of-tune note has been selected, and is about to be corrected
using Pro Tools Pitch Shift plug-in, which is a destructive plug-in.|
Like with manual rhythm correction, you need to select and separate the bad note. Gauge whether it sounds flat or sharp; you could even run it through a tuner to see exactly how far off it is.
Next, set your pitch shifter to compensate (it will usually be a small amount, much less than a full semitone), and perform the shift. Listen to it; if the correction is too little or too much, undo it, change the setting slightly, and try again.
A static note is the easiest kind to pitch-shift. If a note is bending or sliding out of tune, it’s a lot harder to get the pitch shift to sound natural. You could isolate the out-of-tune section and correct that, but the transition will likely be too obvious. Be particularly careful when working with vocals; because they’re mixed louder than other mix elements, their imperfections will stand out more.
Mike Levine is a New York-based musician, producer, and music journalist, and the former editor of Electronic Musician.