Mezzetino the musician (or Mezetino) is another Commedia dell'Arte secondary character, maybe the mask came first, but situations are so interlaced with Carnival, that it becomes very hard to tell.
The Mezetino name comes from the wine Half-Litre-Measure (Mezzo di Vino), which gives the idea that he is quite interested into drinking and having a good time.
Mezetino is original from Bergamo like most Zannis, is an adept schemer and trouble-maker, violent if necessary, flirts with Isabelle quite a bit, and the animals images on his dress may give the idea he is quite an animal himself, a "natural", wearing a sexual power symbology.
In another version of this same image, there is some text added, that goes like this:
"Du Mezzetti Sem chi fomnina bella
Che vè vol da de Berghem la Cappella."
"We are two Mezzetinos who to a lovely woman
We would like to give the Bell Tower* of Bergamo."
* Going quite wild here, but just giving a look to the
Cappella di Bergamo - the Church's main tower in Bergamo - it may become clear how foul this double meaning is ;-)