There are a few interactive music design exhibitions at the Museum of Art and Design in NY. I thought it was very well curated and the pieces were thoughtful rather than gimmicky. My personal favorite were the musical instrument/jewelry pieces, probably because I am obsessed with ceramics. Why do I like it? It was well constructed, that may be a bourgeoisie value, but there it is. The inputs and outputs did not seem random, but were the exploration of a single concept or gesture.
For me it is ok if a mapping is not necessary – I dont think mappings can be necessary or imperatives – but if they reveal something about the concept they are exploring then I am satisfied. And in this case, I believe the artists succeed. Plus, its fun for the kids!