The organ of St Thomas's Church is a renovation of former instruments, with much new pipework, completed by Guilbault-Thérien in 1991. The style of voicing used makes possible the accompaniment of the large body of English church music, as well as most of the repertoire.
It has 48 stops over three manuals and pedal. In 2004, two digital 32 ft stops were added to the Pedal division, providing stirring deep notes (and a gentle massage to choristers who sit in the Decani stalls).
A Festival Trumpet stop, housed behind the Lady Chapel on the north side of the Choir, was added in 2008. A trilogy of organ concerts marked the addition of the stop. John Tuttle played the first one on May 14, 2008, opening with the Fanfare by John Cook, then playing the Bach Passacaglia and the Serene Alleluias by Messiaen, as well as the Second Symphony for Organ by Louis Vierne. The organist and choirmaster of Coventry Cathedral, Kerry Beaumont, played on May 21, and included a marvellous improvisation on ‘Salve Regina.’ On May 28, Aaron Tan, a young virtuoso who is also studying nano-engineering at the University of Michigan, played a stunning recital including music by Sir Ernest MacMillan, Petr Eben, Bach, Dupré and Vierne.