A. I have some releases which states BOB performed all instruments and then Oh but MIKE was on the keyboards and DICK on one of the guitars.

B. I have other release wich say Musicians : Micheline et Jean-Claude.

Instead of guessing we should be able to copy this BOB info truthfully from the booklet and having an instrument-empty instrument AR (like what we have for vocals) for B and specific attribute ALL INSTRUMENTS for A.

Unfortunately, it is actually kind of a MBS-3391 revert for B.