Like the Serialists, Mr. Perle argued that if the 12 notes of the chromatic scale were treated equally, they would yield greater expressive possibilities than the seven-note major and minor scales that had dominated Western harmony for centuries. The difference between Mr. Perle’s method and strict Serialism, though, was that he did not insist on predetermined and rigorously ordered tone rows (or note sequences). He was equally free in his use of rhythms and dynamics.