It would be very nice if the relationship editor had default performance roles. That is, when you add an artist for a role, it would pre-fill the relationship with a best guess based on existing ARs.

e.g. a lot of the time a violinist, conductor, or singer/soprano will only or primarily perform that role. So it would make sense to guess that every time they are added, they will probably be "performed instrument: violin", "conducted" and "performed vocals: soprano".

Of course, when an artist does different roles roughly equally it's probably better not to guess (but if they always perform an instrument, at least pre-fill "performed:instrument")