Leading British composer and conductor Oliver Knussen has died unexpectedly at the age of 66, his publishers have announced.

“Faber Music is deeply saddened to announce the death of Oliver Knussen, our beloved House Composer of over 40 years,” they said. “Knussen was one of the world’s most eminent and influential composer-conductors and leaves behind him a body of work of crystalline concision, complexity and richness. His impact on the musical community – both in the UK and around the world – was extraordinary, and is a testament to his great generosity and curiosity as a musician, as well as his unfailing love and deep knowledge of the art form.”

A highly regarded composer, Knussen famously suffered intermittently from writer’s block and was a ruthless suppressor of his own music when he felt it didn’t come up to scratch. He still, however, leaves behind a respectable legacy of over 30 musical opuses. As a conductor, he championed a wide range of modern (and not so modern) composers and was a regular presence in the recording studio where he built an enviable discography. As an artistic director and curator, he influenced numerous festivals and ensembles, and as an educator he inspired many younger composers including Mark-Anthony Turnage and Julian Anderson.

Oliver Knussen was born in Glasgow on June 12, 1952, though he soon found himself in London where his father was principal double bass of the London Symphony Orchestra. Something of a prodigy, he began composing at age six before going on to study composition with John Lambert between 1963 and 1969, and with Gunther Schuller at Tanglewood.

As early as 1966, the LSO spotted their bassist’s son’s talent and commissioned his First Symphony. The 15-year-old Knussen himself stepped in to conduct its premiere at the Royal Festival Hall on April 7, 1968 after the scheduled maestro, István Kertész, became ill. Two weeks later, he made his American debut when Daniel Barenboim invited him to conduct the work’s first two movements in New York. Shortly afterwards, he received a commission from Benjamin Britten for the 1969 Aldeburgh festival. Britten would go on to encourage the fledgling Knussen from then until the older composer’s death in 1976.

Known for his intricate, sometimes knotty music, Knussen’s best-known work is probably Where the Wild Things Are (1979-1983), a one act opera based on Maurice Sendak’s popular children’s book of the same name. He followed it up in 1985 with a companion piece, Higglety Pigglety Pop! for which Sendak again provided the libretto.

In the 1980s, Knussen was invited to become co-artistic director of the Aldeburgh Festival, a post he held from 1983 until 1998. He subsequently made his home in Snape. He was also invited to head up the contemporary music program at Tanglewood, a job he carried out between 1986 and 1993.

His Second Symphony premiered at the Proms in 1984, but after that his output slowed for reasons mentioned earlier. Landmarks would include Flourish with Fireworks (1988) and 2006’s Requiem: Songs for Sue, a musical tribute to his late wife.

Among his most important associations, his close ties with the London Sinfonietta (he was Music Director from 1998 to 2002), were probably the most important, generating a string of recordings on Deutsche Grammophon, from Stravinsky and Copland to Takemitsu and Carter. “Olly helped create, and then lead as Music Director, an era at the London Sinfonietta that is now a shining part of our history,” said Andrew Burke, the orchestra’s Chief Executive and Artistic Director. “His performances with us are some of the best we have ever given. And his music some of the most inventive and engaging we’ve ever played. He was a man of towering, uncompromising musical integrity.”

Much honoured, Knussen was appointed a CBE in 1994 and was the recipient of the Royal Philharmonic Society’s Conductor Award in 2009. In 2014, he became the inaugural Richard Rodney Bennett Professor of Music at the Royal Academy of Music in London and in 2015 was awarded the Queen’s Medal for Music.

Only last month, Knussen was in action at the Aldeburgh Festival, conducting music by Birtwistle, a long-time and close colleague. “Knussen was one of the most important musicians of our time,” said Snape Maltings chief executive Roger Wright. “His concerts… just a fortnight ago were another reminder of his stature as a conductor, bringing fresh insights to 20th century repertoire and premiering new work by fellow composers. His support for younger generations of composers through his mentoring and nurturing was unique, and his compositional legacy is remarkable – a relatively small output but one which is of outstandingly high quality.”

Meanwhile, friends and fellow musicians have paid tribute:

“Awful news: the death of Oliver Knussen, one of the truly iconic figures in British music, and a wonderful, warm, witty, generous man. He conducted the premiere of The Protecting Veil – one might not automatically associate him with that style, but he ‘got’ it immediately,” tweeted cellist Steven Isserlis.

“Very sad to learn of the death of Olly Knussen. An extraordinary composer and conductor, an exceptionally inspiring man. I got to know him just a little bit 25 years ago in Tanglewood. We were so proud that he agreed to come and conduct our orchestra in Stockholm. A great loss,” tweeted conductor Daniel Harding.

“Olly was the greatest musician I’ve ever known,” said Composer Mark-Anthony Turnage. “He was a major British composer and conductor – by far the best of his generation, with ears even better than Boulez’s. He was also my closest friend, with such a kind heart, and was like my Dad. The loss to me but also to us all is incalculable.”