Music: Pioneer at 56

Leipzig music lovers gasped when Henry Cowell sat down at the piano: the young American composer was slamming the keys with his forearms. When he continued the attack with forearms, fingers and fists, Leipzigers got to their feet, and the anti-forearm group tangled with the let's-hear-him-out crowd. The police, that evening in 1923, finally led a score of the noisiest demonstrators away.

Since those days, pioneer Modernist Cowell, now 56, has run up his own musical scores to more than 800, including eleven symphonies, and his music has been played around the world. None...