B
bagatelle - literally, a "trifle" - a short unpretentious composition.

ballade - a piece of a romantic type, usually in ABA form, combining dramatic and lyrical characteristics.

band - a large ensemble consisting mainly of wind instruments.

barcarolle - a lyrical boat song usually in moderate 6/8 or 12/8 time, and ABA form, supposed to be derived from the songs of the Venetian Gondoliers.

bar, barline - a vertical line drawn through one or more staves to indicate a measure. Bar also means measure (e.g., a four-bar phrase).

bar form - a form in three sections, the first of which is ( AAB ).

barocco - eccentric, bizarre.

bass - a voice, instrument, or part in the low register.

Bass Clef- also known as the F clef.
                     
bassa - low, deep

basso - the bass part, the lowest male voice.

basso continuo - the instrumental figured-bass part in an ensemble played by one or more bass instruments and a keyboard instrument.

basso ostinato - a persistently repeated theme in the bass register.

beat - the unit of time in metric music. In time signatures, the upper numeral indicates the number of beats per measure.

ben, bene - well, good.

bene placito - at will, at pleasure.

ben marcato - well marked or accented.

berceuse - a lullaby, a quiet piece generally in moderate 6/8 time, with a rocking movement in the accompaniment.

binary two-fold/binary form - a form of two divisions or sections (AB).

bis - twice - (the passage is to be repeated).

bitonality - use of two different keys simultaneously.

bolero - a quick Spanish dance in 3/4 time with accompaniment of castanets.

bourree - a French or Spanish dance, usually in quick duple time, starting on an upbeat; similar to the Gavotte, and often found in the old suites.

brass - wind instruments which produce tone by vibration of the lips.

bravura - spirit, skill.

breve - a double whole note breve equal to two semi-breves or whole notes.

brillante - bright, sparkling.

brio - vigor, spirit.

broken chord - the tones of a chord played consecutively, usually according to some pattern.

buffa, buffo - comic, humorous.

burlando - in a playful manner.