The piano piece “Mask” is central to understanding the developmental trajectory of Arnold Bax’s musical language, which was reaching maturity between 1912 and 1914. This hitherto hidden gem represents a fundamental milestone within the path of Bax’s stylistic and aesthetic evolution. It was written on July 22, 1912 (the same month Nympholept was composed), approximately one month after the arrival in London of Serge Diaghilev’s celebrated “Ballets Russes,” for whom Bax had written the unperformed and unpublished ballet Tamara, composed between July and November 1911. On a personal note, Bax had married Elsita Sobrino in 1911, and in January 1912, his first son, Dermot, was born. It was therefore a period of significant and enriching personal and artistic stimuli…..From Ennio Caironi’s Introduction to this first edition. “Mask” was dedicated to Gustav Holst’s cousin, Mary Lediard. Hitherto thought lost, we have Nick Barnard to thank for discovering the manuscript in a sale at Hanson’s and having the forethought to copy it from the auction house’s catalogue.