Harry Gabb's tenure of his posts as organist at the Chapels Royal and at St Paul's Cathedral was marked by a consummate professionalism and graced by a warmth of personality which endeared him to generations of choristers, lay-vicars and organ students, as well as to an extraordinary range of non- musicians. His handling of the enormous and widely dispersed St Paul's organ was admired, while his unflappability and secure technique were strengths in coping with the demands of playing at state occasions.
Gabb won a George Carter Scholarship with the Royal College of Music, where, as well as organ lessons, he studied composition with Herbert Howells. In 1929, at the early age of 20, he was appointed sub-organist at Exeter Cathedral, as assistant to Dr (later, Sir) Thomas Armstrong. In 1937, Gabb was appointed Organist and Master of the Choristers at Llandaff Cathedral, but German bombing forced the end of services in the cathedral building, and shortly afterwards he left for war service with the Royal Armoured Corps.
For part of the war, Gabb was stationed in Egypt which allowed him to play the organ in Cairo Cathedral. After demobilisation he returned briefly to Llandaff, before moving to London as sub-organist at St Paul's Cathedral in 1946, forming a memorable musical partnership with Sir John Dykes-Bower. In 1953, Gabb was appointed to HM Chapels Royal, and he held these two organist posts until 1974. He played at several state occasions (including Sir Winston Churchill's funeral, and as one of the organists at the Coronation) as well as at the weddings of Princess Anne and Princess Margaret. At the latter of these, it gave him particular pleasure that his son, Roger, was carrying the Colour of the Guard of Honour outside the entrance of Westminster Abbey as he was playing inside.
Part of the secret of Harry Gabb's success was the trouble he took in preparation. He was a notoriously early riser (a habit he maintained to the end of his life), and maintained a strict practice routine, spending usually two hours a day at the St Paul's instrument before a (usually sociable) breakfast. He was justly proud of his pedal technique and took especial pains that his students should be similarly proficient. In the tradition of organ as orchestral substitute, Gabb was in demand for oratorio and choral concerts, and his intuitive rhythmic sense was striking: with his highly practical skills and love of accompanying large congregations, he made hymn-singing a musical, rather than a routine, event.
Gabb was sought after as a teacher, and was for many years Professor of Organ Playing at Trinity College of Music, in London. Latterly though, as the organ world changed around him, towards historically aware performance practice and modern musical idioms, Gabb remained immutable: he would listen stoically to contemporary works brought to him by his pupils, but his comments would be centred on playing technique. However, in his own favourite repertoire he excelled and gave much to his students.
Occasionally, Gabb could be diverted into showing off his considerable skills as a theatre organist - sometimes a useful tactic for students who had practised less assiduously than their teacher.
On retirement in 1974, he and his wife Helen moved to Chobham, where he became parish organist. One sensed that this most unassuming of men enjoyed his retirement work as much as any other part of his professional career. Harry Gabb had also served as a Special Commissioner for the Royal School of Church Music, and as a Council Member of the Royal College of Organists.