Problem with the "Repeat" effect

I’m trying to use the “Repeat” effect to repeat a riff over and over that I want repeated through a song. The problem is, after a few repetitions, it gets out of sync with the drum track, and gets further and further out of sync.

The obvious possibility is that the selection I’m repeating is just a fraction of a second too short or long and that fraction is being compounded over multiple repetitions until it becomes noticeable.

But I’m doing something that I think should keep that from happening. Before applying the repeat, I repeat play the selection along with the drum track. I figure if the repeated passage sound okay rhythmically, with no “hiccups” – no unwanted fractions of beats or incomplete beats – then the repeated passage should be the right length. Could it be that my subjective perception isn;t good enough?

Could the latency correction setting be causing the repetions to be out of sync? WOuld setting it to zero fix the problem?

If it’s relevant, the drum track was also created using the repeat effect – by sampling two bars from a CD and repeating them many times.

That’s the two bowling balls on the sidewalk problem. No matter how carefully you start two bowling balls running down the sidewalk, they’re not going to in sync then they reach the Tesco/7-Eleven (I just made that up).

The only way to manage that is loop the composite, not the individual pieces. AFAIK.

Audacity Version 2 has some sync and management tools. I haven’t looked there yet.

When you repeat play the selection it will be repeating exactly the same amount of the “riff” track as drum track, so even if the selection is fractionally short/long it will be both parts that are fractionally wrong (by the same amount) so they will not drift out of synch.
Listening to loop play will allow you to get close to the right length selection, but an error less than about 20 milliseconds will be virtually impossible to hear (until it is compounded over multiple repetitions).

Okay, thanks everyone. As I suspected, it’s got to do with an error in the length of the selection that you simply can’t hear until it gets compounded.

Come to think of it, I suppose I should have realized that, given that I am very familiar with the two Steve Reich pieces “Cone Out” and “It’s Gonna Rain.” They both involve tape loops that sound like they;re in sync at first and then gradually move out of sync. But Reich wanted it to happen.