It's not often you get a chance to buy a slice of the former Soviet Union's secret musical history. But this Thursday Sotheby's is putting up for sale a collection of hitherto unpublished love letters from the young Dmitri Shostakovich (right) which should help to shine a little more light on a still shadowy corner of the portrait of the composer which first began to emerge in the West with the publication, in 1979, four years after his death, of his posthumously ghost-written (and possibly spurious) book of memoirs, Testimony.

Intriguingly, this sometimes passionate correspondence between the then 28-year-old (and married) composer and his 20-year-old German teacher, Elena Konstantinovskaya, began in June 1934, only months after the sensational premiere of his soon to be banned opera, The Lady Macbeth of the Mtsensk - a sexually explicit tale of adultery, multiple murder and suicide which Shostakovich once intended to be the start of an operatic trilogy on the theme of Russian womanhood.

The sorry end of the affair with Elena seems to have put paid to that: he went back to his wife, while she found herself expelled from the Young Communist League and imprisoned. Later she went to fight in the Spanish civil war and married a Spaniard, before returning to the USSR, becoming head of languages at the Leningrad Conservatoire and writing a student textbook - to which Shostakovich contributed a preface.

The 21 letters are expected to fetch between pounds 10,000 and pounds 15,000.

10.30am 26 May, Sotheby's, 34-35 New Bond St, W1 (071-493 8080)

(Photograph omitted)