The late Victor Borge was not only an accomplished classical pianist but a hilarious comedian to boot. In the early 1940s, Borge (originally Børge Rosenbaum) escaped the Nazi menace in Denmark, travelled to America, and started performing his now-famous routines. One of those skits is called Phonetic Punctuation, where Borge creates different silly sounds for the punctuation that he encounters as he reads a romantic story.
http://www.youtube.com/watch?v=6bpIbdZhrzA
Borge also did duets and a particularly funny one involved singer Marilyn Mulvey who valiantly tried to perform Caro nome from Rigoletto, despite the many interruptions from the pianist. See that clip after the jump.
