This instrument, built by Marr & Colton, a prominent builder of theatre organs, is by all reports the largest, unaltered church organ built by this company. When the need for theatre organs came to an abrupt halt with the introduction of the 'talkies' in the late 1920s, Marr & Colton began to explore the church organ market. The organ in St. Alphonsus is not a theatre organ modified for church use. It was designed by David Marr to be a church organ in specification, sound, and operation. The pipework of this organ is scaled and chosen to produce the sound one would expect from a church organ. There are no tibias, skinny strings, or phonon diapasons. Unification is moderate, and the organ contains eight straight stops, one of which is a Mixture III made of principal pipes.

The organ was rebuilt in 1969 by Parsons Organ Company without any changes. Since that time, the organ has been subject to emergency repairs, and periods of neglect. The instrument is in need of rebuilding, but remains playable.