Strange problem - momentary sonic glitch, every track

[StickPlayer]

I reported this maybe a year or more ago in version 7, but here it is in 8.2.1.

The"glitch" is just an instant of pure noise - very, momentary. But here's the weird part: every track that is playing will have the identical glitch in the identical spot.

Solo a track (ANY track actually making sound at that instant where the glitch is) and you'll hear the glitch at the one spot in time. Move the track and the glitch stays in the same spot in time (relative to the start of the entire project - not relative to any track). Samples, instruments. frozen tracks. With or without any FX. All the same.

When I had this last time, I ended up having to make an entirely new project and recreate EVERYTHING to get rid of it. This is not really acceptable. There's just too much to think about here in terms of patches, samples, automation.

And here's something else to think about. When I reported it last time, it was on a completely different system. Nothing whatsoever is the same. Not the operating system, and certainly none of the hardware. Complete reboot has no effect.

Ok, so here's what I've done to isolate it. I took one of the two tracks playing, and soloed it. Playing back over the affected section, the glitch is very obvious. This is a track with Ableton's "Mixed Choir Ahh/Ohh" on it, with no other fx. I then froze ALL other tracks. The glitch went away. I then put tracks back, one at a time. Luckily, the very first track put back- the other one playing at the same time, seemed to reintroduce the glitch. Unfreeze that other track, glitch plays (on the soloed choir track). Freeze that track, glitch is gone.

Ok, so what is on that other track? Sample files and the Ableton "Reverb-Concert Hall(TrueStereo) fx. That is all.I turned off the reverb, played back - still glitches. Understandable - I think turning it off means it is still "running" that verb, just not mixing it in? Maybe not, but in any case, it had no effect.

So then I attempted to delete the verb - at which point it disappeared from the track, and now I am watching the spinning "wait" circle in Windows 7 - for waaaayyyy too long. Yup, trying the delete hung Ableton completely. So I killed the process - or I thought I did. But it won't die. That's kind of difficult to do in Win7, but there it is - the undying process (apropos as the piece has the name "undying", but somehow I doubt that's the problem). Remember, this was from a fresh reboot, with nothing else started other than Firefox (and the gazillion other processes Windows starts anyway, but which always run without this problem in Ableton... usually).

So that's as much as I can do - have to post this and restart again. Yes, I have a fair number of plug-ins loaded - several instances of East/West's current "Play VST", Ozone 4. But mostly Ableton instruments/Fx.

From what I can see, this is some kind of bug in the playback engine. The CPU isn't close to maxing out. In fact, at that instant in the song there are two very lightweight tracks making sound. The only thing on the master is a tempo change maybe 20-30 bars earlier.

Will post more if I figure something out.

[StickPlayer]

More info...

Ok, so the reverb is not the problem. But here's the thing - the track causing the glitch is just a bunch of samples. Actually, one sample file, chopped up with varying transposition on each piece. And it looks like THAT is the problem. The glitch occurs exactly at the boundary of two samples, where the sample ending is transposed up 8 semitones, and one starting is up 9 semitones.

If I get rid of (delete) the first sample (so there's NOTHING on the track) and leave the second one - glitch! If I take out the second sample - no glitch.

So.. it isn't the fact of having to transition between 8 and 9 semitones between two samples - nope. It is the mere fact of having to transpose THAT sample 9 semitones up. That's all it takes to cause a glitch EVEN when the track with the samples is muted. Which makes sense, because muting I'm sure doesn't stop the sound engine from computing the playback of the track, it just doesn't mix it in. But nevertheless, the engine has a serious FAIL at this point.

I also tried changing the amount of transpose - 10 up still gives the glitch. 8 does not. 11 does. Not conclusive, but looks like 9 or higher, on that sample, glitches the entire playback.

My final solution was to just consolidate that sample, with its transpose. That of course means the engine has no real-time transpose to do. AND it fixed the problem. I can also "solve" it by freezing the offending track - the glitch is then gone. But this way I had the least effect on the overall track and the ability to manipulate it.

The conclusion is that live sample transposition can have a bad interaction with overall sound output of the sound engine at the start and end of some transposed samples. I seriously hope you can consider looking into this. I did take the two tracks, and just moved the very short, affected section to another part of the project where there was nothing else - and repro'd this just fine.

Thus I now have a very, very short sample project that can create the problem. I can package that up with it's samples (would be only one, except it uses the choir instrument so has all those samples). Where should I send that, to whom, with what info?

[Ableton_David]

Hi, please get in touch with Ableton technical support about this: http://www.ableton.com/support. Thank you.

[StickPlayer]

I've sent a link to this thread and the project reproducing the problem to support@ableton.com

-Oz