I'm not sure what film set this was from, although I did see another photo from this series, with Marcello Mastroianni holding the cello.
Does anyone out there have any further info? I don't believe this was a Fellini film, yet I could be wrong. The photo was from Tazio Secchiaroli (Fellini's still photographer, also the person who inspired the character of Paparazzo in "La Dolce Vita").