The great Cathedral organ which now serves St. Mark's has gone through a number of evolutions over the years. In 1928, a four-manual organ was installed by the Welte Organ Company. The instrument, designed by Charles Courboin, organist of St. Patrick's Cathedral, New York City, and Stanley Avery, organist of St. Mark's from 1909 to 1949, was well-known for the breadth and beauty of its ensemble. An 8-foot bombarde was added by the Aeolian-Skinner Organ Company during the tenure at St. Mark's of Edward Berryman (1949-1959).

The distinguished Canadian organist Gerald Bales, at St. Mark's from 1959 to 1971, supervised the addition of a four-manual console by M. P. Moller in 1961. In 1964, a complete rebuilding was carried out by the Moller Company. Twenty-five ranks were retained from the 1928 Welte organ. The original wind chests were rebuilt, with the exception of the great wind chests which were replaced with new lower-pressure chests.

In 1976, Howard Don Small, organist at St. Mark's Cathedral from 1971 to 1998, arranged to add a French-type trompette to the swell division, place two ranks of principal pipework in the choir division, and add a 32-foot bombarde octave to the pedal division.

As part of the celebration of the 125th year of St. Mark's, the organ was completed in 1983. The long-awaited positiv division was installed on the west side of the chancel, a principal chorus was added to the antiphonal division, and a two-manual console was placed in the gallery. These additions were designed, built and installed by the firm of Gould and Sons, Inc. The high-pressure festival trumpet in the gallery was installed and voiced by Timothy Patterson. There are four blowers, one to main organ, one to positiv, one to gallery, and a small high-pressure blower for the festival trumpet.

Between 1993 and 1995, Gould and Schultz, Inc. completed a major refurbishing of the instrument, including a thorough cleaning of all the pipes, a revoicing of the swell reeds, a releathering of the reservoirs in the front organ, and a releathering of the shade actions.

In 1996, under the supervision of Canon Musician Howard Don Small, the Schantz Organ Company of Orrville, Ohio, replaced the aging Moller console with a new four-manual solid-state console. Provided as well was a remote and portable one-manual console without pedal designed for playing in continuo in instrumental ensembles. The latter's keyboard contains six general pistons that duplicate the first six on the main console.

Taking generous advantage of the latest technology, the large console has full MIDI capability, giving the organist control over optional synthesized sounds; a transposer; ninety-nine memory levels; a great/choir manual transfer for performing the French repertoire; one fixed and one programmable sforzando; one fixed and three programmable crescendos; a switch allowing swell pistons to operate the pedal pistons; and a sequencer which replays the organ exactly as it has just been played, including changes in registration and swell shades. The keyboards are of bone and rosewood. Of primary consideration was the need for a low profile design to facilitate sight lines between organist and conductor. The whimsical drawknob engraved "Divine Inspiration" in the great division was prompted by the eponymous murder mystery written by Jane Langton involving organists and organs in the Back Bay area of Boston.

With the refurbishing complete and the new console in place, two stops are still desired for St. Mark's organ in the future, as funds permit. An harmonic flute, so frequently called for in French organ literature, would add a warm foundational tone to the great organ, and a true 32' bourdon would contribute solidity and beauty to the pedal organ. If you would like to make a gift towards these two very special additions to the Cathedral organ, please contact the church office.