*obbligato / obli'gahtoh/ adj said of a musical part or accompaniment: not to be omitted. [Italian obbligato obligatory, past part. of obbligare to oblige, from Latin obligare]

*Definition from The New Penguin English Dictionary

**obbligato
ob-bli-ga-to (ob-li-ga-to) adjective - not to be left out; obligatory (used of a musical part or accompaniment that is considered prominent but usually ornamental).

**Definition from www.wordsmyth.net