I’m still learning tricks and techniques in SynthV pro but so far I cannot find anything that lets me follow a backing track’s tempo change.
If the backing does a simple step-change from, say, 100bpm to 140bpm or, more likely (and I guess harder to implement) if the backing has accelerando or rallentando. 
Would anybody be able to enlighten me please?
You can double click on the measure bar at the point where the tempo changes and it’ll change the tempo from that point for the rest of the song.
「いいね！」 1
So that is blissfully easy then, I just required that bit of insight.
I guess I could handle accel by either incremental tempo increases or a single increase somewhere mid accel (to try to make post-accel voice and backing sync properly) and deselecting snap to grid whilst constructing that part.
Thanks 