Just a follow up. I've been away.
The feature
"Pause playback until midi"
doesn't work out for me.

While it does generate the real tracks when the song loads, and waits for midi or space bar - that works fine.
What doesn't work if you turn this on:
if you try to use any of the midi conductor mini-notes like to skip ahead or back a bar - it immediately stops playing and pops up the yellow dialog about waiting for midi input. Sometimes I need to jump ahead or back a few bars, so I have some of the midi controller notes set to let me do this.

I also can't start songs with Ctrl-numpad-2 - it just ignores this.

Oh well - I'm back to setting it generate on loading of the song, and immediately stopping it, only to hit replay when it's time to really start - and "wishing there was a feature" to do this.