This long-awaited third volume of composer Benjamin Britten's remarkable letters covers the years 1946-51. Fresh from the astonishing success of his great first opera, ''Peter Grimes, ''Britten was vital to the post-war rebuilding of the arts in Great Britain with his visionary work as a composer, conductor, and performer. With his partner, the celebrated tenor Peter Pears, he founded the Aldeburgh Festival, which eventually grew into the international festival that it is today, and the English Opera Group. He also toured widely in Europe and the United States as a pianist and conductor. During this time he wrote many of his best-known works, including the operas ''Billy Budd, Albert Herring, ''and ''The Rape of Lucretia. ''Britten's correspondents include literary figures such as Christopher Isherwood, Edith Sitwell, E. M. Forster (the librettist for ''Billy Budd''), and Edward Sackville-West, as well as musical colleagues from around the world including Ernest Ansermet, Francis Poulenc, Aaron Copland, and Igor Stravinsky. This volume of selected letters represents one of the richest and most innovative periods of the composer's creative life. His daily concerns and the unique era in which he lived are vividly evoked by the comprehensive and scholarly annotations, which offer a wide range of detailed and fascinating information. Donald Mitchell contributes a superb introduction.