Tried this with Adobe's phone support and got shut down because it was a "how-to" question, not a technical one, and I should look on YouTube or use a program more dedicated to audio. I strongly suspect it's actually a bug in Premiere, but maybe someone can help me understand the problem better.
I have 2 audio tracks, which each have their own subsequence in them. The subsequences are the same length. They have the same sequence settings (and are the same Hz). They contain clips from 1 source audio file each, both of which are identical in format and length, and each subsequence contains a complex set of edits. They are aligned on the timeline and perfectly synchronized to each other so that they sound how I want them.
If I use Speed/Duration to increase the speed of both clips by the same amount, they remain perfectly synchronized.
But if I check the box "Maintain audio pitch", they stop being in sync with each other.
I can't understand what could be causing this to happen. If audio clips start playing at 00:10:00 on both subsequences, and I double the speed, those clips should both start playing at 00:05:00, regardless of whether or not I'm maintaining audio pitch. That's clearly not happening, but I'm not sure exactly what is happening.
The tech support rep insisted that this was a "how to" problem, and refused to explain to me how the "Maintain audio pitch" option could affect whether the audio is synched or not. I'm just looking for any insights anyone has as to what is actually happening so I can pre-empt the problem in the future.
The audio seems to start going out of sync around the 8-10 minute mark of a clip. So what I did was just create a new sequence out of the 30-minute video I was working with, and then go in and make a slice every 5 minutes or so. Then when I preview the sequence the audio presumably "corrects" itself every time there's a slice! Not an ideal solution, but it definitely does the trick!