Exactly. It does require a few samples of track delay. I didn’t know why that is. Maybe the DAW’s idea of what 89.1 bpm is is ever so slightly different from OP1’s idea.
I intend on making a demonstration video after messing about with this technique a bit more.
I’d be pretty surprised if this works in general, because some sort of saturation/limiting must be happening in the overdubbing process (otherwise: you could keep overdubbing again and again and eventually the summed level of the signal would overflow/clip).
This means overdubbing can’t simply be adding the existing+new signals, it must (in some cases anyway) perform some amount of re-scaling of the volumes, meaning that this trick won’t work in general.
(It’s possible they have enough headroom internally to avoid having to do this for a while, I guess it depends on how hot you’re hitting the tape.)
Anyway that’s a really clever trick, I’m surprised it works!