Cost of an instrument: measure it with a chord held, at every declared rate #78

What is missing. The cost arm measures a plugin at rest with noise in. An instrument costs nothing until voices play, so its cost figure says nothing. #72 plays instruments for the real-time-safety count only.

Done when. For a plugin with a note input, the cost arm holds a fixed chord (the note sweep's CHORD, native/clap-qualify.c) for the whole measurement at every declared rate, the document says the cost was taken with notes held, and a fixture whose cost grows per voice reads higher held than at rest.