[1] He learned music (piano and harmony) from his father and organ with Otto Barblan in Geneva.
[1] After his father's death in 1899, Mooser went to Russia and worked for ten years in St. Petersburg as a music critic for the French-language publication "Journal de Saint-Pétersbourg".
[1] In 1909, Mooser returned to Switzerland and until 1962 he was a music critic for the Geneva newspaper La Suisse [fr], and for some time its editor-in-chief.
In 1915, he founded a cycle devoted to contemporary music, Les auditions du jeudi.
His main works are Annales de la musique et des musiciens en Russie au xviiie s. (1951) and Visage de la musique contemporaine (1962), as well as numerous articles on various musicological themes.