And yet, given a composer of genius, even that can produce something intriguing – as is proved by a new CD of scores for documentary films written by Benjamin Britten. They were composed during the mid-1930s for the famous GPO Film Unit, led by one of the great names in documentary filmmaking, John Grierson. The unit's first offer to Britten came in the nick of time, in April 1935.

Philip Reed, the Britten scholar who prepared the scores for the new CD, feels that the experience was invaluable in other ways too. "It taught him how to capture a mood or setting in the shortest possible time," he says. "Also the tiny budget for music meant that Britten was restricted to just a handful of instruments. The experience of conjuring lots of different colours and textures with small resources I think was invaluable in later years when he was writing his chamber operas."

Alongside The King's Stamp are two scores which always come up in any discussion of film music: Night Mail and Coal Face. These incorporated spoken and sung texts by W H Auden, the brilliant, intellectually combative young poet who left his job as a prep school master to join the unit's payroll as scriptwriter. Britten was captivated and over-awed by Auden, while Auden was struck by Britten's "extraordinary musical sensitivity in relation to the English language. Here at last was a composer who set the language without undue distortion."

Less well known among their collaborations, but equally ingenious musically, is the score to The Way to the Sea. This is ostensibly a salute to Portsmouth's glorious naval history, but it already has the satirical note that Auden and Britten later struck more insistently in Our Hunting Fathers. Altogether this CD shines a fascinating side-light on a great composer in the making."