Lambertus Reinier de Leeuw's mother and father were both psychiatrists: Cornelis Homme 'Kees' de Leeuw and Adriana Judina 'Dien' Aalbers. From age 7 he took piano lessons. He studied music theory and piano at the Amsterdam Conservatoire and composition with Kees van Baaren at the Royal Conservatory of The Hague. He taught at the Royal Conservatoire of The Hague. He was a well-known conductor and pianist performing mainly contemporary music. He was the founder of the “Dutch Charles Ives Society”. Since 2004, he was a professor at the Leiden University in 'performing and creative arts of the 19th, 20th and 21st century'. In 1974, he founded the Schönberg Ensemble. They mainly focused on performing works by the Second Viennese School and the avant-garde. He composed the piece Etude for the strings of the ensemble. De Leeuw regularly conducted the Netherlands' major orchestras and ensembles, including the Royal Concertgebouw Orchestra, New Sinfonietta Amsterdam, Residentie Orchestra The Hague and ensembles such as the Netherlands Chamber Choir, the ASKO, the Netherlands Wind Ensemble, and the orchestras of the Dutch Public Radio. In the 1995–96 season, he was the centre point of the 'Carte Blanche' series in the Concertgebouw Amsterdam. He was involved in the organization of the series 'Contemporaries' at the Concertgebouw Amsterdam. He was a regular guest in most European countries and the United States, in Japan and Australia. Reinbert de Leeuw was involved in various opera productions at the Dutch National Opera in Amsterdam as well as with the Nederlandse Reisopera. Productions included works by Stravinsky, Louis Andriessen, György Ligeti, Claude Vivier, Robert Zuidam and Benjamin Britten. In 2011, De Leeuw conducted Schoenberg's monumental Gurre-Lieder, which was the realisation of an old ambition of his. In 1992, he was guest artistic director of the Aldeburgh Festival and from 1994–1998 artistic director of Tanglewood Festival of Contemporary Music. De Leeuw was artistic advisor for contemporary music with the Sydney Symphony Orchestra, and from 2001 to 2010, he served as artistic leader at the Nederlandse Orkest- en Ensemble-Academie. On January 13, 2020, he held his last concert in Muziekgebouw aan 't IJ. On February 14 of the same year, he passed away at his home in Amsterdam, aged 81, survived by his brothers, Kees and Hans de Leeuw.
De Leeuw made his recordings mostly for Philips, Koch or Nonesuch. One of his last efforts in the studio was, however, for Alpha Classics: a remarkably sincere, piano-accompanied reading of Liszt's own late and devotional Via Crucis, reflecting De Leeuw's faith. He had previously recorded Via Crucis twice, in the 1980s for Philips and in 2012 for Etcetera.
