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Phase issues during tempo automation

Posted: Sun Apr 11, 2021 2:43 am
by Papa Gionni
Greetings all! I have used Live for many years without ever encountering this problem before so I hope someone can help.

I am recording two different tracks of guitar from a guitar cabinet simultaneously, into a session that has a bunch of tempo automation. The microphones are on two different speakers in the same cabinet, both mic'ed very close (basically on the grille cloth). Being mic'ed so closely there should not be any phase issues, and indeed there aren't. I can listen back to the tracks in unison and they sound fine... UNTIL the master tempo changes and it seems to throw the guitar tracks into utter phase mayhem. They phase and warble very extremely for a few seconds, then settle into an equilibrium that isn't actively warbling anymore but sounds hollow and like there is some amount of phase cancellation.

The tracks were recorded to the metronome simultaneously at the same master tempo with the same automation. No warping or tempo changes have been introduced after tracking. In theory it seems that during playback the tracks shouldn't even be affected by the master tempo automation, they should play the same either warped or unwarped, since it's just playing back the audio exactly as it was recorded. But in addition to this weird phasing issue, it would seem that something else is subtly amiss, because when I turn "warp" off on the tracks, they slightly change in length.

I could just turn warp off and they would both be fine, but then they are slightly out of step with the drums and the master arrangement. Plus I'm slightly spooked that there is something truly fishy afoot. This is a very strange issue and I am completely at a loss to explain it. I've done this exact same thing many times before without any issues. Anybody here know what's going on?

BTW I am using Live 9 if that is pertinent.

Re: Phase issues during tempo automation

Posted: Wed Apr 14, 2021 7:39 pm
by Papa Gionni
It turned out that the gaps caused by unwarping the clips were pretty insignificant, and I could easily just patch over the gaps in audio and it sounded fine. For this project that's good enough, but I'm still super confused why this would happen.

I read somewhere on this forum that if your default warp mode is set to Complex rather than Beats, it treats the audio differently as it is being tracked. I don't know if that's true or not, and I set my default warp mode to Beats but it didn't really seem to fix the phasing issue.

Anybody have any ideas on this?

Re: Phase issues during tempo automation

Posted: Wed Apr 14, 2021 9:22 pm
by Tarekith
Complex and Complex Pro warping will alter the audio even if your recorded audio is at the same tempo as the project. All of the other warp modes are completely neutral as long as the audio file tempo is the same as the project.