This date refers to the completion of the full score. The 1973 catalogue of Britten's works (published by Boosey & Hawkes) gives the date of the work as 'March 1959', which is probably the completion date of the composition draft (which is undated). The composer announced the work's completion in a letter to George Malcolm dated August 24 1959, but the full score is annotated 'Sept 1959'. Britten had accepted the commission on 30 October 1958.
Agnes Giebel sop, Elsa Cavelti contr, Peter Pears ten, Heinz Rehfuss bass, Basler Kammerchor, Sterk'scher Privatchor, Basler Kammerorchester, Paul Sacher cond
Orchestra: 2 fl (II=picc), 2 ob, 2 cl in B flat, 2 bn - 4 hn, 2 tpt in C, 3 trbn, tuba - timp, 4 perc (trgl, tamburo militare, tamb, cymb, Chinese block, bd, t-t, xyl, glock, bells in C) - 2 harps (II ad lib), pf (=cel ad lib) - str
By the University of Basel.