chuckebaby
I know this can be done easily enough in sonar, but why ?
Why not give us a pitch wheel for crying out loud.
Noel would need to give a definitive answer, but I highly doubt the audio engine was set up initially to do that...and I suspect it would be difficult to change now. Back in 2000, I don't think computers were powerful enough to do real-time audio stretching without horrible artifacts.
Frankly I would rather not vary speed in the project itself because even with today's DAWs, you can still hear artifacts (although the situation is much, much better than it used to be). This is why I'm into the old school varispeed tape-type change, where pitch and tempo changes track each other - no artifacts. For maximum fidelity, I'll keep doing a project at whatever tempo I started, and if I need to do speed changes, will do them to the final, mixed 2-track.