Why is the ninth month called September?
musical instruction, 1724, from Italian obbligato, literally "obligated," from Latin obligatus, past participle of obligare "to bind" (see oblige). In reference to a necessary accompaniment by a single instrument.
(Italian: "obligatory"), in music, essential but subordinate instrumental part. For example, in an 18th-century aria with trumpet obbligato, the trumpet part, although serving as accompaniment to the voice, may be as brilliant in its writing as that of the voice itself. The term obbligato accompaniment has a more specialized meaning in some 18th-century music (see accompaniment)