[1] He studied as an undergraduate at Oriel College, Oxford, from 1889 to 1892, taking a fourth class in theology and becoming a Bachelor of Music and Master of Arts in 1896.
He was one of the editors of Tudor Church Music, ten volumes published by Oxford University Press in the 1920s with the support of the Carnegie UK Trust.
Fellowes was honorary librarian of St. Michael's College, Tenbury from 1918 until 1948, and during this time he arranged and catalogued the musical library of Sir Frederick Ouseley.
Fellowes' editions of English Tudor church music represent a very significant contribution to 20th Century musical scholarship, bringing to new prominence composers such as Byrd and Orlando Gibbons, whose work was thus made accessible to composers and scholars, notably Ralph Vaughan Williams, whose revision of The English Hymnal was influenced by study of these themes in Fellowes' editions.
Oriel College, Oxford, maintains a collection of his papers that includes a letter to his mother relating his eyewitness account of Queen Victoria's funeral, his work on Tudor Church Music, letters from Adrian Boult, Edward Elgar, Gustav Holst, Herbert Howells, Hubert Parry, John Stainer, Charles Villiers Stanford, Leopold Stokowski, Ralph Vaughan Williams, Henry Walford Davies, and Henry Wood.