Baynes began his career as an organist and accompanist at the age of 13. He later held the position of chorus master at the Theatre Royal, Drury Lane, and he gained international recognition as a composer while serving as music director to John Tiller from 1910 to 1914. His fame centers around his waltz compositions, some examples of which are Destiny (1912), Ecstasy (1913) and Mystery (1914). He also composed songs, religious works, piano pieces and orchestral music. One of these was a work he composed for the victory thanksgiving service at Westminster Abbey in 1919, Endure to Conquer. His other credits include conducting and composing for several London theatre productions, and from 1924 to 1929 he served as music editor to Boosey & Hawkes. His later years were occupied with conducting his own orchestra, playing his arrangements for broadcast. He also made recordings for Columbia and HMV.