Arthur Knox Duff (13 March 1899 – 23 September 1956) was an Irish composer and conductor, best known for his short orchestral pieces such as the Handel-inspired Echoes of Georgian Dublin. His career also encompassed senior positions in the Irish Army School of Music and in the music department of Radio Éireann.
Duff was born in Dublin to John William Duff, a native of King's County (now County Offaly), and his wife Annie Kathleen Hickey. Duff was a chorister in Christ Church Cathedral, Dublin and studied at the Royal Irish Academy of Music under Charles Herbert Kitson. He completed his education at Trinity College, Dublin where he obtained his primary degree in arts and music. In 1942, he was awarded a doctorate in music following an examination. Duff was initially drawn to the ministry of the Church of Ireland but abandoned his religious studies before the final examination.
Duff had a varied career in music as a solo performer, conductor, arranger, producer, and composer. He later became an author and playwright, although he remained most famous for his music.
He first came to public prominence in his early twenties for his organ recitals in St. Matthias's Church in Dublin.
In 1923 Duff joined the Irish Army and was commissioned as a second lieutenant. He was promoted to lieutenant in 1926. He served as bandmaster in the Army School of Music and conductor of Army no. 2 Band based in Cork. Following his resignation from the army in 1931 Duff turned to the theatre, writing incidental music for a number of plays produced in the Abbey Theatre, including works by W. B. Yeats and Denis Johnston. His own play, Cadenza in Black, was produced at the Gate Theatre in 1937.