Bach and the Voice. Bach's vocal writing has the reputation for being unforgiving. Singers complain that he treats the voice too much like an instrument, expecting them to negotiate difficult intervals and long lines of semiquavers more suited to the violin orthe keyboard. Over the last 40 years choirs have become smaller in response to the researches of the early music movement, but did Bach expect his cantatas and Passions to be sung "one to a part"? Ivan Hewett looks out some examples of idiomatic and unidiomatic vocal writing in Bach's music, and asks, when it comes to choirs, does size matter?