Flex Time edits don't bounce correctly?

Question

Level 1

4 points

Flex Time edits don't bounce correctly?

Hi there,

today I was editing the timing of some acoustic guitar in Logic Pro 11 using the polyphonic (auto) Flex Time algorithm. I duplicated my track and used the bounce in place function to consolidate my edits only to notice that the waveform of the bounced version didn't perfectly line up with the waveform of the track that had Flex Time active. That was somewhat concerning to me as I would hope my edits would commit exactly the same as when I was working on them and so I performed a null test, flipping the phase of the bounced track with the gain plugin and discovered that the tracks didn't cancel each other out in any parts with flex markers and also a little bit after the flex markers. Has anyone come across their Flex Time edits not bouncing correctly? perhaps I'm doing something wrong here. Also, some other strange behaviour that I noticed, which I had never encountered before, was that my audio was sometimes being stretched outside the boundaries of my anchor flex markers. Thoughts?

Thanks!!

Posted on Mar 30, 2025 2:40 PM

Reply

Answer 1

EddieGrey

Level 4

1,318 points

Mar 31, 2025 8:44 PM in response to ToneTinkerer

Sir,

You have to understand that bouncing and editing and are not the same functions and are dependent upon many particulars viz.

Export Features that you enable/disable
Plug-ins on the channel strips themselves may use different algorithms (not fixed algorithms)
Plug-Ins you may have on the Stereo Output

If one of these things is off, null test will not work. To be transparent, bouncing to audio freaks me out to and I sometimes hear differences so I totally get it. Just take your time and try using less and less plug-ins to perform these test. Best of Luck!

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Answer 2

ToneTinkerer Author

Level 1

4 points

Mar 31, 2025 8:31 PM in response to EddieGrey

Hey Eddie! here is a photo that shows that once bounced, the waveforms don't remain exactly the same as when working on them in Flex Time. One track was bounced with the bounce in place function and the other was exported as audio. I also posted my settings for each of these functions. At first I thought maybe the difference was just visual, but a null test proved that there was a difference in the rendered audio compared to the active Flex Time edits, however slight it may be, which doesn't seem right to me for a precise task such as editing

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Answer 3

ToneTinkerer Author

Level 1

4 points

Mar 31, 2025 9:41 PM in response to EddieGrey

Hey Eddie,

Thanks for your reply. However, there were no plugins at use in my logic session and, feel free to correct me, but I believe all of my settings when bouncing were correct. Theoretically, without any other variables at play, the rendered file should be exactly the same as the work I was doing in Flex Time and null right?

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Answer 4

ToneTinkerer Author

Level 1

4 points

Mar 31, 2025 11:28 PM in response to EddieGrey

Right, but one of those windows was for export as audio, the other for bounce in place. Those two bounces weren’t being nulled against each other; I was attempting to null each, one at a time, against the track that had Flex Time active. Plus isn’t ‘include audio tail’ only relevant if a time based effect such as delay or reverb is in use on the track and turning on include audio tail just includes the decay of the effect?

anyhow, I’ll play around with various settings and see what happens. Maybe it’s an issue of latency between the track with flex time turned on and the bounced version of that? Curious and open to any other thoughts! Thanks :)