A part of some double reed instruments. The bassoon, english
horn, oboe d'amour and baritone oboe all use a bocal, but the
oboe does not. The bocal is a slightly tapered metal tube that
connects the reed to the wooden body of the instrument. Bocals are
made from sterling silver, nickel silver, or brass. On the
bassoon, the bocal includes a tiny hole near the place it inserts into
the instrument. This is the hole for the whisper key, which is
closed for pitches in the lower registers.

Bo"cal (?), n. [F.]

A cylindrical glass vessel, with a large and short neck.

© Webster 1913.