[2] He spent three years at the RCM and then, on Sir Walter Parratt's advice,[2] applied for and won the organ scholarship at Worcester College, Oxford, graduating in 1902.
[3] In 1908, he designed the organ for Emmanuel Church, West Hampstead, in consultation with Walford Davies[4] who gave the first performance.
[5] The Dean of Worcester College, William Henry Hadow, had strongly supported Colles to use his gifts with the written word in the field of music criticism.
[2] His writing was marked by its "comprehensive taste, sure and fair judgment, and ... unfailing tact and humanity that tempered even his severest strictures".
According to one obituarist, his assistant critic A. H. Fox Strangways, Colles's task was "to put in some sort of showing, on people and things that 'ought to find a place there', apart from any intrinsic interest they might or might not awaken; he was, in fact, a general tidier-up of half-remembered persons and topics".
[2][3] Colles was an examiner for the Associated Board of the Royal Schools of Music, visiting Australia and New Zealand in that capacity in 1939.
[2][3] In early 1943, he was instrumental in arranging for the release from internment on the Isle of Man of the composer Egon Wellesz, to enable him to take up a fellowship of Lincoln College, Oxford.