Assertion: concertina's button | /r/CapableOf | do unisonoric
Facets:
Source sentences:
text: : refers to an instrument on which each key or button produces two notes, as does bisonoric (a term recently coined on the model of the French and German ) double-action : refers to an instrument on which each key or button produces a single note,  as does unisonoric (recently coined as the counterpart of bisonoric)