That's why I need a script. I'm not looking for the tape-stop kind of effect.
I was thinking of using the GrooveClip pitch control to do the pitch. I'm basically trying to write something that approximates Reaper's "playback rate" slider, though this would only do discrete input values, no automation obviously.
The reason I was hoping to write a script was so that it could change: the project tempo(s), turn all clips to GrooveClips with 'stretch to tempo' to do the time-stretching and then GrooveClip's 'pitch' and/or 'fine pitch' parameters to mimic the change in "tape speed". The pitch would be calculate from the amount you wanted to increase or decrease the tempo.
I'm not sure it'd be possible with CAL and I've just seen that it was actually deprecated!
I think I'll have to look into Python but I've got a sinking feeling...