Audio from two sources doesn't sync

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kelsonz27

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Hi, I'm not really sure if this is the right place to post this, but I'll try. I did some basic recording with my band the other day and we used 2 portable recorders on either side of the room planning to mix the two audio files later. When I put them both in Audacity to try to sync them up, they line up for the first minute or so of the song and then slowly get more and more out of sync until the end of the song (after about 3:00 in) the two are so out of sync that it is unlistenable. Does anyone know what could be causing this or if I could fix it?
 
What kind of recorders are they?

If they're analog tape that's your answer I'm afraid.
 
Assuming they're both set to record at the same sample rate and there's no funny conversion going on or anything,
there's probably just a discrepancy between the clocks in the two devices.

I can't say this is fact, but I'd guess being digital devices, the discrepancy should be consistent.
What I'd do is clap loudly once at the end of a recording, then in audacity, I'd time stretch one of the audio files until the two match.

This is a 2 second job in Protools; I don't know how audacity handles it.

I'm not sure that there's any other way around it to be honest, but maybe someone else knows.

With professional audio gear, you'd generally slave all devices to run from one master clock. That avoids this kind of problem.
 
I recently used some scratch vocals a friend made singing along to the mix using his iPhone. Had the exact same issue. Like you probably already did, lining up the start was easy as the drums come in first and I could lineup the wav pattern to start with the project files. Then I ended up chopping the recording in non-critical spots, quick fading the cut edges, then nudging them a couple milliseconds back. Every 30-60 seconds seemed enough to keep the recording in line and listenable.
 
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