A reed stop of 16' pitch (also 8' according to Irwin), so named because of its supposed resemblance to the sound of the Renaissance instrument of the same name. According to Locher it is a free reed, usually without resonators. Irwin claims it has full or half length inverted conical resonators of gentle taper. Audsley characterizes its tone as midway between the Bassoon and the Trombone; Irwin describes it as �both brasslike and distinctly reedy�. Wedgwood simply considers it a synonym for Double Basset Horn. Strony describes the Serpent of the theatre organ as follows: The Serpent is an extremely loud and thin English Post Horn. Originally, Kimball built several of these ranks, the most famous one being in the Wiltern Theatre in Los Angeles, California. This experiment by Kimball was not musically successful; it was too thin and had too many undesirable trash harmonics. A standard English Post Horn would have been much more effective. In recent times, other pipe manufactureres have built Serpents. These examples are much more pleasing, and are more like large English Post Horns. The most famous and musically successful example was built by Austin Organ Compnay and was installed in the Organ Stop Pizza Restaurant in Phoenix, Arizona. This instrument is currently (1991) installed at the Krughoff Residence in Downers Grove, Illinois. While this Serpent is thin and loud, it is also focused and refined. And it contains all of the right harmonics. Some modern instruments have an English Post Horn and a Serpent. Usually the English Post Horn is more conservative and the Serpent is thinner, louder, and brighter. The Serpent appears in the pedal division at 8' pitch; and in the manuals at 16' TC and 8' pitch.

Serpent 16', 2nd (upper) Pedal; Cathedral of Ulm, Münster, Germany; Walcker 1856. Serpent 16', Schwell-Pedal; Cathedral, Riga, Latvia; Walcker 1883 (restored 1983). Audsley describes this as �a species of Double Corno di Bassetto�.

Serpent 16', Choir; Symphony Hall, Boston, Massachusetts, USA; Aeolian-Skinner 1950. Serpent 16', Positif; Davies Symphony Hall, San Francisco, California, USA; Ruffatti 1984.

Serpent, Pedal; Castlegate Congregational Church, Nottingham, England. Serpent 32', Pedal; Blackburn Cathedral, Blackburn, Lancashire, England; Walker 1969.

Serpent 16', Choir; Chancel organ, Riverside Church, New York City, New York, USA; Aeolian-Skinner and others, 1947-1995. Serpentino 16'; Church of Sanctissimo Crucifisso, Como, Italy.