Sentence:  Rameau 's Six Concerts en Sextuor , recorded by L ' orchestre de chambre Pierre Menet ( BAM LD 046 ) , turn out to <WSD>be</WSD> harpsichord pieces arranged for strings apparently by the composer himself . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)