violoncello obbligato

OBS: Violoncelle (...) ital., violoncello.
OBS: Obbligato: (...) terme qui s'applique à une partie vocale ou instrumentale dont l'exécution revêt un caractère d'absolue nécessité (par ex. ""violino obligato"" (...)

OBS: violoncello (...) although similar in construction to the violin, the ""cello"", as it is familiarly called, differs in having relatively deeper ribs and a shorter neck.
OBS: Obbligato: A second melodic line which is played with the basic melody (...) It is usually an instrumental part.