Does anyone know if it is possible to temporarily transpose a sequence while holding a note and it revert back to the original key when letting go of the note?
That’s quite confusing the more I read it… 
If you’re just talking about hands on with the A4, I’m sure you have to use the mini keys to set the transpose amount, then press the key to go back to your home key…
I think I understand you now, you mean can the keyboard act in momentary mode instead of latching… I don’t think you can.
Yes momentary, that’s what I mean (wasn’t sure of the correct term).
10.12.10 TRACK TRANSPOSE
To transpose, press and hold [TRNS] and press a [KEYBOARD] key. Select a different octave range to transpose to by pressing [UP] or [DOWN]. After having performed a transpose, a little pop-up window will show how many semitones the transpose consists of.
The notes of the tracks are transposed according to the TRK KEY NOTE and TRK KEY SCALE settings, found in the NOTES SETUP menu covered on page 35. The transpose is an offset to the set key note, meaning all note trigs retain their original note values after having been transposed. If for example the key note is set to a C and [KEYBOARD F1] is pressed, the transpose activated tracks will be transposed +5 semitones.
So the manual makes no reference to it working any other way than how it does, latched.
Nice idea though, might be worth dropping in the feature requests.
I find myself doing this often on transitions where I’ll take a bass part up 2 octaves, then drop it back down with the beat… you have to be quick and nimble to get it lined up in time, having it momentary would make that easy.
Thanks for looking into it. Yes I also like to record a bass line then transpose in small amounts on the occasional note to make variations.