Autocorrelation tool?

[Warren Sirota <wsirota@wsdesigns.com>]

Like many of you, I often record my experiments and improvs at home and then later want to release them. Obviously, there always has to be some editing - after all, how else do you present the golden 7 minutes without necessarily subjecting your listeners to the 45 minutes of noodling on different patches that preceded it?

Well, take whatever position you will in the argument of "honest documentation of a performance" vs. "good listening", but I personally don't want to have to cringe for the next 30 years every time I hear that horrible note near 3:57, so I'll generally throw away the stuff that I hate. So I'm not pure, so sue me. :-) 

So what I usually end up doing in my editing process is to keep it minimal - cut out the bad stuff, every once in a while maybe graft a bar from someplace else. 

If I have the foresight to save a loop (I'm using SooperLooper at the moment) while I'm recording (and every time I record a new first loop), then my editing life is a dream. Want to drop 16 measures of an ill-advised sound choice in the midst of an otherwise compelling piece? In most DAWs, if the DAW's concept of a measure is the same as yours, it's pretty trivial - select the measures and snip. the loop parts fit together with no clicks because length cut was an exact multiple of the loop length. If you don't have the DAW tempo synced to the loop length, you have to go through a fairly painstaking process of trying to find the exact start and end points of each snip. Editing is therefore highly discouraged.

What DAWs need to sync their concept of tempo to yours is typically an audio file consisting of exactly one loop (or some known integral multiple). So if I save a loop using whatever tool I'm in, then I'm home free.

OK, finally, the question: what if I haven't done this? The loop file (I record in multitrack, so the live input is separate) contains a lot of areas where there is no change in the loop for a while while I'm playing. Are there any tools available that could autocorrelate a file like this and tell me how many samples there are in a repeating section? 

Thanks,
Warren