In 1950, composer Leroy Anderson wrote "The Typeriter"--a short and funny orchestral piece that uses a typewriter as a musical instrument. You can watch a performance of it here. And you should because it's really amusing.
In that version, a professional percussionist played a mechanical typewriter. Chris Gregg and Bruce Molay, however, programmed an electrical typewriter to do the same thing and type a specific, coherent message in the process! Hack A Day describes how it works:
An Arduino Uno converts serial over USB output to a bit stream ready to clock into the shift registers. On the computer side, [Chris] wrote up a basic CUPS driver which allows him to print from his Macbook. The perfect demo for this project turned out to be musical. Click past the break to see The Smith Corona perform “The Typewriter Symphony”, by Leroy Anderson. This may be the first time this particular piece of music has been performed with actual words being typed, rather than random keys.