Reinbert de Leeuw has established a reputation as one of the most eloquent and persuasive conductors of contemporary music. He became well known in the 1970s for his interpretations of the piano music of Satie, but since then he has focused his energies largely on conducting the works of contemporary composers, particularly mavericks who bucked the tradition of serialism that dominated the new music scene for nearly half a century following the Second World War. De Leeuw is most closely associated with the music of Olivier Messiaen, György Ligeti, and Louis Andriessen. Each of the three employed musical languages of considerable complexity and sophistication that is notoriously difficult to perform, but their music is notable for an expressivity and directness of communication that was uncommon in an era when the majority of new music was considered "difficult" by audiences. De Leeuw's grounded understanding of their distinctive idioms and his commanding interpretations make his performances of their music particularly riveting. He has also devoted attention to non-Europeans with a strong streak of individualism, and has recorded works by Americans Ruth Crawford Seeger, George Antheil, Henry Brant, Steve Reich, the Australian Percy Grainger, and Canadian Claude Vivier. De Leeuw has also made a mark as a composer.
De Leeuw was born in Amsterdam and studied piano and theory at the Amsterdam Conservatory and composition at The Hague Conservatory. From his student days, he was interested in new and experimental music. He was one of the founders of the Nederlands Charles Ives Society, and in 1969 he wrote a biography of Ives with poet J. Bernlef. In his mature career, he has focused almost exclusively on works ranging from the early modern period through the contemporary. In 1974, he founded the Schoenberg Ensemble, based in The Hague, which specializes not only in the composers of the Second Viennese School, but a broader repertoire ranging from the late 19th into the 21st centuries. The group has performed and recorded so extensively with another new music ensemble, the ASKO Ensemble, that the two officially merged, and de Leeuw has remained one of the principal conductors. He has been guest conductor at the Aldeburgh Festival, and with the Royal Concertgebouw Orchestra, the New World Symphony, the RIAS-Kammerchor, the Netherlands Radio Chamber Orchestra, and the Netherlands Opera; artistic director of the Tanglewood Festival of Contemporary Music; and artistic advisor to the Sydney Symphony Orchestra.
As a pianist, de Leeuw has recorded works by Satie, Bartók, Stravinsky, Shostakovich, Ustvolskaya, Messiaen, and Górecki. He was most active as a composer during the 1960s and '70s. His works include several orchestral pieces, chamber music, and an opera, Reconstructie, based on the life of Che Guevara, written in collaboration with Louis Andriessen, Misha Mengelberg, Peter Schat, and Jan van Vlijmen. In 2003, de Leeuw wrote Im wunderschönen Monat Mai, a radically free reimagining of 21 lieder by Schubert and Schumann, for singer and orchestra.