And then I went into Band in a Box, and I had a song laid out that needed a country style with acoustic strumming. And I picked a style with a Recommended Tempo of 85, but my song is at a tempo of 98. I soloed the Acoustic guitar Real Track and I could definitely hear the warbliness at that tempo. So then I reset the tempo at 85, the Recommended Tempo, and I could not detect any artifacts, shakiness or warble in the track. So I must conclude too that, as Rob H. said, if you stay within the recommended parameters the track should be OK. I should say too that the only kind of track that I have heard this kind of warble in is an acoustic strumming track, from which I might conclude that the more polyphony there is in a track then the less flexibility there is with it. BUT, when I brought in the Real Track from the HD earlier into Melodyne I had also raised the tempo by quite a bit and the track was still pristine. So I guess there are many more factors at play within the program itself, and this is more complex than just raising and lowering the tempo along with changing the pitches. I also tried increasing the tempo by the same amount with an acoustic fingerpicking style and I really couldn't hear anything that would be an artifact or anything. Anyway, it was fun experimenting and getting to know what the limitations are. I guess to really know that I would have to raise, as well as lower, the tempo of an acoustic strumming track by 1 bpm at a time until I hear it starting to warble.
I had considered the possibility that this was caused by the USB streaming from the HD to the computer but it has only been detected by me in acoustic strumming Real Tracks. But I don't use the program as extensively as a lot of people do, just for a track here and a track there, so I haven't gotten that deep into it yet.

Fivehands