It is Piano Time on Main Street.
Another great thing about Disneyland has always been the music. Whether it is the area music in the background as you walk through the park or live music like the Disneyland band or The Dapper Dans, or the piano players on Main Street. The music of Disneyland is something that sets the mood. So enjoy it whether you are just passing by or actually stopping to take it in. It is one of the little details that make Disneyland so Magical.
Video from You Tube Mr DAPS