Thank you all for the helpful responses to this question.
But to continue, I am rather perplexed at learning that MARC bib 382 is being mapped to a note field. Since the LCMPT (Library of Congress Medium of Performance Thesaurus) has recently been released as linked data, why would we want to be so “string-y” about medium of performance in Bibframe? Also, I have noticed that, in current transformations, MARC bib 048 (the “traditional” place for coding instrumentation before upstart 382 came along) is not being mapped at all. (Of course, some kind of programmatic conversion from 048 to 382 may be in our future.) Moreover, I want to be thinking also about new data we may soon begin to generate, outside of transforming what we already have. This aspect of music resources is crucial.