William Pearson, an avant-garde American opera singer whose powerful baritone and stage presence inspired several European composers to write music structured around him, has died at age 61.

Pearson died in his Cologne apartment of a heart attack on June 18, said Franz-Josef Heumannskemper, his companion.Pearson arrived in Germany on a Fulbright scholar in 1957 to study at the Musikhochschule in Cologne.

Classically trained, Pearson sang Porgy in the first European production of Porgy and Bess in Helsinki, Finland, in the late 1950s. He later became the favorite baritone for "dada evenings" put on by European composers, singing falsettos in the surreal, often grotesque sketches of what later became known as Vocal Theater.

He worked with composers such as Dieter Schnebel, Mauricio Kagel, Gyorgy Ligetis and Silvano Busotti.

Pearson was cremated and buried in late June in Cologne. He left no family.