Oxford Chamber Music Festival – described by Oxford author Philip Pullman as “a national treasure” – returns this week with its biggest programme yet and a strong focus on the environment.

The festival, which runs at various Oxford venues from tomorrow to Sunday, is based on the theme of Elements, and features an eclectic mix of concerts and fringe events that celebrate the four essential elements of earth, water, fire and air.

It is characteristic of a festival that, since its inception, has challenged and inspired audiences, constantly pushing the boundaries with its quirkiness and sense of the unexpected.

“From the start I wanted OCMF to be more than a series of concerts,” says Priya Mitchell, who founded the festival in 2000. “My desire was to provoke, surprise and query preconceptions about classical music concert experiences, and I hope we have achieved that by sparking our audience’s imagination and curiosity.

“My hope is that the elusive fifth element – the realm of the spirit – builds a subliminal bridge to connect musicians and audience through the music experienced together, combined with the intensity of being exposed and transported to so many incredible sounds and emotions in a short time.”

Priya has gathered together some of the world’s top chamber musicians such as oboist Nicholas Daniels, organist/conductor Tom Fetherstonhaugh, cellist Matthew Barley and rising star Sheku Kanneh-Mason.

Sally Beamish is this year’s composer-in-residence and plays viola in some of the concerts, which include the premiere of a short clarinet and violin duo, The Flittin’, written to celebrate Gerry Mattock’s 90th birthday.

“I was thrilled when Priya invited me to be composer-in-residence for her festival this year,” Sally says. “The music that Priya has chosen is a cross-section of many aspects of my work. It is a great joy to be included, not only as a composer but as a player as well.”

The opening concert, Songs of Earth and Air, features Sally’s The Book of Seasons alongside Vivaldi’s The Four Seasons, Vaughan Williams’ The Lark Ascending and Tchaikovsky’s Rococo Variations.

Other highlights include Bach specialist Pieter Wispelwey playing Bach’s Six Suites for Solo Cello at the Sheldonian Theatre, an Ariel-themed concert at the SJE and the festival’s first-ever concert at Christ Church Cathedral, Eternal Elements, which includes music by Bach, Berio, Faure, Marcello and Sally Beamish.

The festival ends with a river trip with a concert and brunch, and a concert at Worton Organic Farm.

There is a strong education focus this year, with a schools concert at the Town Hall – hosted by Alexander Armstrong – and a recital at the University Church by university’s organ scholars.

“I see what happens as a collaborative, beautiful, creative havoc, fusing meetings of hearts, minds and souls,” says Priya.

“I do everything I can to create a sense of magic and endeavour to conjure up a musical spell that binds players and listeners together in a week-long community. The motto is Music plus Oxford equals Alchemy!”

* Details from ocmf.net