NOTATIO

this is a long held chord, end of a piece, and I want each string instrument to be repeating up/down bowing individually, without syncing with the other instruments. The idea is to create a sort of "crowd" sound.

I have to use as few words as possible, obviously, and I'll be translating it into French, so it can't be anything too esoteric vocabulary-wise.

Any suggestions?

Something like this? I think that's what I've done that has achieved what you are asking for.

You might make that ‘independently ad lib.’ if you feel it's safer, or even ‘individually ad lib.’.

My idea: (VП freely)