<p><strong>Adjective</strong></p><ul><li>obligatory or indispensable; so important that it cannot be omitted.</li></ul><p><strong>Noun</strong></p><ul><li>plural: obbligatos, obbli­ga­ti.<ul><li>an obbligato part or accompaniment.</li><li>a continuing or persistent subordinate or background motif.</li><li>a subordinate part of a solo.</li></ul></li></ul>