Often when I edit a track in a project, the synchronization with the rest of the music is unacceptably lost. I tried using the “Sync-Lock Tracks” feature, but that option does not let me, say, add an effect to a track without adding it to the other tracks. I think Audacity is a super app, so surely I’m overlooking something. Is there a way to, say, add reverb to a track or section without the raw wave shifting out of sync with the other tracks?
Please give an actual step-by-step example. We can’t see what you are doing.
I apologize if I haven’t been clear.
Here’s just one example…
Drum track: the waveform clearly reflects the beat of the bass drum, snare drum etc.
Guitar track: the start of a riff lines up vertically with the beat of the bass drum.
Apply the “Change Pitch” effect to a section of the guitar track and watch the wave shift leftward, advancing the timing. The two tracks are now out of sync. During playback, the particular guitar section now plays back too early.
Not all the effects in Audacity cause timing instability: the “Amplify” tool can be applied repeatedly without altering the timing.
It’s not a big deal to use an effect that causes instability of timing if the entire track needs to be re-aligned; but if adding effects to sections of tracks then correcting the loss of synchrony becomes painfully time-consuming. I must undo the effect or zoom in and then cut and paste tiny parts of the of tracks to re-align the wave with the drum track.
You can easily replicate this example by duplicating a track, applying the “Change Pitch” effect to the beginning of one track and watch the wave jump to the left. The track with the applied effect will play back early and be out of sync with the other track.
Surely I’m overlooking something, and it’s possible to apply various effects to sections of tracks without ending up with a multichannel recording that sounds like the musicians have poor timing or recorded the tracks without using monitors.
“Time stretching” is a complex task. The method used by “Change Tempo” and “Change Pitch” involves chopping up the audio into tiny slices, stretching them, then stitching them back together again as neatly as possible, There are a lot of compromises in getting the pieces to fit back together again after they have been stretched. As it says at the bottom of the page in the manual ( Audacity Manual )
Change Pitch is a time-stretching effect, because it defies the normal expectation that to lower the pitch of the audio it is necessary to reduce its speed (and thus its length) and vice-versa. As with any time-stretching effect, some audible distortions will be expected at more extreme settings.
Due to weaknesses in its algorithm, Change Pitch does not keep the length exactly as before. This makes Change Pitch unsuitable for changing the pitch of individual very short notes. To avoid this problem, you can use Effect > > Sliding Time Scale / Pitch Shift… > instead, setting initial and final pitch change to the same amount.
Sliding Time Scale / Pitch Shift… uses a much more complex algorithm, which takes longer to process, but is much higher quality than the older “Change Pitch” and “Change Tempo” effects. It also allow a variable amount of pitch shift and/or tempo change.