Old West Church, built in 1806, was designed by the prominent New England architect Asher Benjamin. The organ, one of the more modest three-manual organs made by C. B. Fisk, has proven to be remarkably flexible for the interpretation of a wide range of musical styles. Economy dictated re-use of several sets of rebuilt pipes, largely in the Swell and Pedal, from a previous Cole instrument.

The main case is a re-working of a mahogany case built about 1830 and attributed to Thomas Appleton. The case, which had been painted, was salvaged from a church slated for destruction in Ipswich, Massachusetts. A new second tower was added to what had been a central tower design, and the Choir case, mounted on the gallery rail, is entirely new. The Great Trumpet 8' was the first set of reed pipes to be made in the then newly-established Fisk pipeshop. As in many Fisk organs from this time, there is a strong French classic influence in the basic tonal design, essentially Alsatian, and most closely related to the Andreas Silbermann organ in Marmoutier, France.

For decades, this instrument has served as the chief recital organ for the New England Conservatory of Music and is among the most beloved of Charles Fisk's works. Under the leadership of Yuko Hayashi, the Old West Organ Society continues to bring leading organists from throughout the world to play and present masterclasses on Opus 55.