So why have we had to wait 65 years to hear another major piece from this remarkably fertile period? Since Britten's death, it has gradually emerged that not only was he prolific - he was incredibly prolific; the Britten-Pears Library has finally finished cataloguing the composer's juvenilia, and the total stands at about 400 items. According to the composer Colin Matthews, who was Britten's amanuensis for the last three years of his life and has edited his early works, there were perhaps 10 pieces that could have been his Op 1, just as there were six string quartets before the official No 1. Other works got laid aside for one reason or another, and the youthful composer was just too busy earning a living - writing music for film and radio, and fulfilling commissions - to revive his early pieces. Some of them, like the American Overture and the Concerto for Benny Goodman, Britten simply forgot; others he did take an interest in, and returned to later on, but perhaps with some degree of inhibition - he once remarked to Donald Mitchell, his publisher, on the revival of Paul Bunyan, that he was "so accustomed to hearing how bad these early works were, he had come to believe it himself". (An echo here of his extremely touchy attitude to criticism - partly sparked off by the regular reprimands he received from pompous critics in the early days for his excessive "cleverness".)
Britten, however, like Elgar before him, had a very strong relationship to his own musical (and non-musical) past, and maintained a distinct fondness for these early works, despite their supposed "badness". So it's not surprising that the process of rediscovery and revival began while the composer was still alive - indeed he began it himself with the Simple Symphony of 1934. In later years, though, his fondness didn't extend to an active personal involvement - he left it to friends and colleagues like Matthews and Mitchell to take up the thread. "I got interested in Britten's early works for the BBC," says Mitchell, "and decided to `rescue' them. So I went off to the BBC Music Library and, by God!, there on the shelves, in folders thick with dust, were the original materials - I was thrilled. I piled them all in the car and took them home. Ben said, `Interesting', but didn't want to look at them. I'm glad they were rescued, though - apart from anything else, we've saved a lot of really worthwhile, enjoyable music."
Paul Banks, the man in charge of the Britten-Pears Library, has had the job of documenting and preserving the Britten manuscripts. He stresses how painstaking the composer was, even from his early days; the myth of prolific fluency is a little misleading. "Like Mozart, he didn't usually sketch, but mapped out music in his head, often while walking, and then would write it down in a fairly complete form, in pencil. Even then, he would go back and `tinker' - the pencil score of Peter Grimes has hardly a page without erasures. Another significant point is that Britten from his tenderest years had a very definite interest in the idea of presentation and publication - one of the juvenile songs has a `fake' publisher's title page."
Out of this great mass of material some real gems have emerged in recent years, such as the Quatre Chansons Francaises, composed while Britten was still a schoolboy, but already showing a genuine musical personality. And early works have turned up from other sources, too, as Donald Mitchell recounts: "Pretty soon after Britten's death, we had some cardboard boxes sent to us that he'd left behind in New York when he returned to Britain in 1941. One manuscript was clearly a big work, the Temporal Variations for oboe and piano - Heinz Holliger now considers it one of the most important oboe works of the 20th century."
The flow of posthumously published pieces has been pretty steady, then, and of high quality. So are there more surprises to come? Colin Matthews talks of a 40-minute ballet score that "could be revived", and also, tantalisingly, of a late set of piano variations intended for Sviatoslav Richter, left unfinished, but "performable as far as they go". Banks mentions also an interesting draft for a Sonata for Orchestra from the 1940s. But Britten's trustees all emphatically deny the charge of creating a "Britten industry" - of "scraping the bottom of the barrel", as Donald Mitchell put it. "There's 10 times more material available, if that's what we had wanted to do," insists Matthews. The majority of the remaining material in the archives is of huge biographical and musicological interest, but this year's Aldeburgh premiere is probably the last big find.
Scored for violin and viola with chamber orchestra, the Double Concerto is a substantial piece of some 25 minutes. "There's a lot we don't know about it," says Banks. "He wrote it in his second year at the Royal College; we don't know why - maybe for himself to play." (The viola was Britten's second instrument.) "Anyway, there's nothing in the diaries to enlighten us. It's not as obviously adventurous as the Sinfonietta - he showed the first movement to his teacher, John Ireland, and the style could reflect his influence. From the manuscript it's clear that he started fluently - the first movement was completed in two days - but the slow movement gave trouble, and he went back to it later; there are quite a lot of discarded pages, and some may be missing, but the final version is extraordinarily neat."
Colin Matthews, who has prepared the performing edition to be heard on Sunday afternoon, confirms this. "Working on it was almost boring - there was nothing to do - it was all fixed already. The score is unique, almost like a fair copy, with the orchestration minutely detailed. I've been totally faithful to his intentions - the texture is very spare, but it's clear that's what he wanted. I only had to add a little bit of development in one place, in the slow movement, where it really did seem to be needed. The whole thing was a sort of blueprint, ready for a performance that for some reason didn't happen."
An exciting musical occasion, then. But what of the ethics? The recent furore over Anthony Payne's projected completion of Elgar's unfinished Third Symphony is a reminder that not everyone approves of rummaging among a composer's, especially a great composer's, musical remains. "It's a problematic issue," thinks Banks. "In the end, it depends on the quality of the work that emerges."
For Mitchell, the process, if judicious, is valuable if only because it can tell us a lot about a great creative artist who is now, alas, no longer here. "For me," insists Matthews, "the dubious area is reviving pieces that were withdrawn, like Young Apollo and the American Overture. Once a composer is dead, it's different; discovering his early work is fascinating in itself, and it adds to the perspective, even if the work is inferior. And Britten was very fond of his juvenilia - I think he would have been pleased"n
Double Concerto premiere: Sunday 2.30pm, Snape Maltings Concert Hall (booking: 01728 453543) and live on BBC Radio 3Reuse content