Follow-up.

I tried it. I opened up the BIAB file, in which I wanted to add a ritardando, in RealBand.

RealBand has a feature similar to what I described in Sonar, called "fill..", to set a beginning and ending time, and beginning and ending tempo, and it fills in a series of tempo changes. I didn't know, however, if that would only work on MIDI tracks, or on Real Tracks as well.

Well, it does work on RealTracks, but not well. Yes, it slowed the tempo down the way I specified. But the sound became very bad, with strange noise added, etc. So even the new time-stretching engine doesn't do that well. Hopefully it will be improved in the future. Of course that might also depend on the real tracks being stretched, and also the amount of ritardando or accelerando. It may work OK for a small change in tempo, don't know. (Mine was a large change, to about half the original tempo.)