The subcontrabass flute is one of the largest instruments in the flute family, measuring over 15 feet (4.6 m) long. The instrument can be made in the key of G, pitched a fourth below the contrabass flute in C and two octaves below the alto flute in G; which is sometimes also called double contra-alto flute, or in C, which will sound three octaves lower than the C flute.
The subcontrabass flute is rarely used outside of flute ensembles. It is sometimes called the "gentle giant" of the flute family because of its gentle sound. At present, the subcontrabass flute is an instrument that must be custom ordered. It may be made out of PVC or metal.
This instrument's unique sound quality, dark tone, and at times sluggish articulation make for excellent solo opportunities.[original research?] A workable range of two and a half octaves the instrument has some projection issues, though the Hogenhuis models designed from PVC can make a fine, vibrant and raucous tone when required. Due to the instrument's bore width (the diameter of the tube is approximately three inches), the sonic possibilities are almost endless, with excellent response to overtones, singing tones, and multiphonics (chord tones). C3-G3 sounds rich and it has great opportunities for dynamic power and accent. A3-D4 The tone becomes less secure and loses some of the lower partials and it is great for blending. E4-C5 has a weaker and somewhat unfocused pitch center which may be a good choice for blend or effect.
The double contrabass flute (or octobass flute), an instrument in the key of C pitched a fifth lower than the subcontrabass flute in G, is sometimes referred to as a subcontrabass flute, as for, example, in the instruments made by Jelle Hogenhuis.