Thanks for the response Robin.
I've attached a screenshot of the effect in Mainstage, including the script. I'll try to explain it better.
I spend a bit of time trying to work out tricks for playing without an audible count-in, as I don't want to hear one live and don't want to wear headphones. I could set a quantise value, but it would have to be a 1/4 note probably, as just relying visually on the song pointer to play the first notes, I'd have wait till I could see the record clip was definitely activated, then play my note.
I could probably do that, so that it would be quantised to the 1 next time around. But It might initially sound a bit off as I likely wouldn't have played it right, and I'll often use a synced delay to reinforce the beat (and maybe I needed it quantised to 16ths for some later stuff, in which case it's even more tricky). And if I play early it won't be recorded at all.
With the system as in the Mainstage/Logic script, I can safely play my chord early before the beat and before reaching the record clip, but it will be delayed from taking effect until the 1. So I guess its a quantisation that's working ahead of time, and shifting my early notes towards the beat. In Mainstage this then will take effect for all notes played early, which might be OK, but it would be quite cool if it worked for only for the count in. Maybe that's all a bit esoteric but I can see it being really useful for me at least!
re the close command, most apps I'm familiar with have 'close', (command C in things like photoshop, or W in Logic/Mainstage), and 'quit', (command Q). So I'm used to closing a file, but having the application stay running. I'll close one song file then open another one without the app quitting and restarting. ALK just has a quit, not a close. These are traditionally different on Mac, in my experience. It's not a big deal, it just feels weird to me to open another song without closing the first...