Misha Mengelberg, a Dutch pianist and composer who approached the jazz tradition with an adventurous spirit and an antic sense of humor, died on March 3 in Amsterdam. He was 81.

His death was announced by the Instant Composers Pool, the Dutch experimental jazz collective that he helped found in 1967. No cause was given, but Mr. Mengelberg was known to have dementia and had not performed in public for several years.

American jazz fans know Mr. Mengelberg best as the pianist on the saxophonist, flutist and bass clarinetist Eric Dolphy’s album “Last Date,” recorded in concert shortly before Dolphy’s death in 1964. He was much better known in Europe, and especially in the Netherlands, where he was one of the leading figures in a thriving avant-garde jazz scene.

Mr. Mengelberg’s dissonant harmonies and unorthodox phrasing were reminiscent of Thelonious Monk, an acknowledged influence. But he also drew inspiration from many other sources, including the composer John Cage and the interdisciplinary art movement known as Fluxus.