obbligato
noun(North American English also obligato)
(plural obbligatos, North American English also obligatos)
(from Italian, an important part for an instrument in a piece of music which cannot be left out 必需声部；助奏 Word OriginItalian, literally ‘obligatory’, from Latin obligatus, past participle of obligare, from ob- ‘towards’ + ligare ‘to bind’.