The organ in its present position was built and dedicated in 1876. It was completely rebuilt in 1915 by William Hill & Son, famous for the organs of York Minster, Birmingham Town Hall and Sydney Town Hall. An addition to the Pedal Organ of 'Trombone sixteen feet' was given in 1925.

The organ is built between the two Chancel arches and, together with the Screen, separates the Chancel from the Jesus Chapel. There are two manuals and pedals of twenty speaking stops and three couplers. Its fine tone is much admired by those who enjoy organ music.

In 1997 a very generous donation made it possible for a major restoration to be carried out by Harrison & Harrison of Durham, and at that time the key action was electrified and a 'mixture' added to the Great Organ.

The choir leads the congregation in the singing of hymns, canticles and psalms. The Choir’s repertoire is large, and embraces anthems, two of which are sung every Sunday at Eucharist and Evensong, and also Cantatas and other works, which are performed on Special occasions. The Director of Music is Michael Crabb, formerly Director of the Southend Boys’ Choir and Southend Festival Chorus.

Membership of the Choir is free and open to all.  New members are welcome, and are given a very simple voice test after one month of attendance at rehearsals and services. Please contact the Director of Music on 01702 298314.

Music at Saint Mary's also includes performances by visiting groups - from Choral Societies to Brass Band Music. Concerts also include occasional Organ Recitals and are usually in aid of the various charities that Saint Mary's supports.