From Philadelphia Museum of Art:
The three masked musicians in this painting represent comic figures from the tradition of popular theater in Italy. This Cubist concert features Harlequin playing a violin, Pierrot witha recorder, and a Franciscan friar holding an accordion. The painting has been interpreted as a nostalgic elegy to a trio of friends: the recently deceased poet and critic Guillaume Apollinaire (Pierrot), the poet Max Jacob (the friar), and Picasso himself as the Harlequin.