I’ve realised that every time I do a save, it gives me about a minute to check this thread and see if anyone’s responded. In fact, I’ll happily take suggestions for anything useful I can do in the 50 seconds while my Mac is locked up. 
PS just tried it and found I can pick up my guitar and practise SRV’s solo from “House Is A Rockin’” three times over in the time it takes my N6.5 project to save. So it’s not going to waste.