Many requests on this forum for varispeed have been phrased as a special effect that lets someone continuously drop the pitch or speed like a tape deck coming to a stop. The current request sounds to me more like "varipitch". That is,
a pitch shift of the mix during playback, and a reverse pitch shift of the recorded part after the recording is completed. Given fairly stable, non variable, A/D & D/A technology of sound cards, the digital "analog" to changing the tape speed is pitch shifting or resampling. Recording technicians might need to take note of the transformations that happen in the digital realm.
My guess is that a simple per-project knob will not do the job; yes, one would like a knob for the parts that need to be shifted, but the part being recorded may be playing through Sonar's audio engine as well (e.g. for effects). Shifting it would be counterproductive, and most likely disturbing to the performer and some others within earshot. Someone may object to percussion sounds being pitch shifted as well, at some point. External midi synths, if in use during recording, would also need real-time pitch shifting. So it may require some intelligence on the recording technician's part to determine which tracks or buses need pitch adjustment, and by how much, and which do not.
Instead of one global varispeed knob, how about a
prochannel knob? Any recording technician could have one on their default track or bus template if they really wanted. Adjust it on whatever mix bus needs it, while running the performer's audio on a different bus that has not been adjusted.
Short of a knob on prochannel, there is already the cakewalk pitch shift effect that seems to work on a bus. It is not production quality (for printing), and changing the pitch knob makes a noise. But
no printing or extra passes are needed to prepare for recording; just fine tuning of the pitch in real time. The recording technician can decide at leisure how to resolve the various pitch requirements in concert with sound quality concerns.
But in X2,
anyone might be able map a pitch-shifting vst of whatever quality they need onto a prochannel fx chain. This may be seen as blurting out a "different" method or a workaround, but since I have never had the need for "varispeed" as described, I am not seeing much difference.
By the way, "speed" is an entirely different story and is not so easily solved by a vst. This would best be called "varispeed", and not "varipitch". A musician might for example need assistance from the recording technician to record their performance at a slower tempo without changing pitch.
(Edit for font changes, no words changed)