Rick Davies, the co-founder and singer of the British rock band Supertramp, who co-wrote some of its biggest hits and lent a biting, world-weary tone to its music, died on Saturday at his home in East Hampton, N.Y. He was 81.

Mr. Davies died from complications of multiple myeloma, a form of blood cancer, which he learned that he had more than a decade ago, according to his wife and manager, Sue Davies.

He was “the voice and pianist behind Supertramp’s most iconic songs, leaving an indelible mark on rock music history,” the band said on its website.

Supertramp achieved a commercial breakthrough in 1974 with its album “Crime of the Century,” and went on to become one of the most popular British groups of the 1970s and 1980s. The album’s hit song, “Bloody Well Right,” opened with Mr. Davies on the Wurlitzer electric piano, and his use of the Wurlitzer became a defining feature of the group’s sound.

Supertramp’s hits included “Goodbye Stranger,” “The Logical Song” and “Another Man’s Woman,” a song in which he often improvised piano solos during performances.