In music, Op. 9 stands for Opus number 9. Compositions that are assigned this number include:
Adams – Chamber Symphony Adès – Living Toys Bartók – Four Dirges Beethoven – String Trios, Op. 9 Chopin – Nocturnes, Op. 9 Dohnányi – Symphony No. 1 Kabalevsky – Piano Concerto No. 1 Larsson – The Princess of Cyprus (), opera in four acts (1936) Rachmaninoff – Trio élégiaque No. 2 Schumann – Carnaval Sibelius – , tone poem for orchestra (1892, revised 1902) Sor – Introduction and Variations on a Theme by Mozart Strauss – Seufzer-Galopp Vivaldi – La cetra