In 1978 the facade that originally covered the organ chamber at Harvard University's Memorial Church became available after being in storage for over twenty years. Charles Fisk saw how well the handsome and elaborately carved casework would complement the architecture of Charleston's First Presbyterian Church and acquired it. The dark oak case and carved pipe shades were restored and expanded to contain the new three-manual Opus 79. The keydesk, located within the case en fenĂȘtre, is oiled mahogany; the natural key covers are of grenadil with accidentals of ivory-capped rosewood.

The organ's tonal structure is inspired by organ building practices of the late 18th century with particular emphasis on the monumental instruments of central Germany, including organs Bach played. This core, along with several stops based on other national traditions, gives the organ a well-balanced eclectic capability, increasing its versatility for recitals and fulfilling its main functions of accompanying congregational singing and choir anthems and playing organ voluntaries. Among the stops adding color and vitality are the French Jeu de Tierce in the Swell and the narrow-scaled, Gottfried Silbermann-style mutations in the Positive. The 16' Great Principal and the 16' Swell Bourdon add gravity to the plenum, the characteristic full sound of the organ, so necessary in a room as large as the First Presbyterian Church. These stops are also available in the Pedal and add to its capabilities for accompaniment.