Double contrabass flute
The double contrabass flute (sometimes also called the octobass flute or subcontrabass flute) with over 18 feet of tubing is the largest and lowest pitched metal flute in the world (the hyperbass flute has an even lower range, though it is made out of PVC pipes and wood). It is pitched in the key of C, three octaves below the concert flute (two octaves below the bass flute and one octave below the contrabass flute). Its lowest note is C1, one octave below the cello's lowest C. This flute is relatively easy to play in comparison to most other large flutes. Despite the tendency of the larger sizes of flute to be softer than their higher pitched relatives, the double contrabass flute has a relatively powerful tone, although it usually benefits from amplification in ensembles.
The Japanese firm of Kotato & Fukushima sell their double contrabass flutes for US$38,000.
Their main use has been in large flute choirs and occasionally in film scores.
A double contrabass flute constructed of PVC, called a subcontrabass flute by its maker, the Dutch instrument maker Jelle Hogenhuis, has the tubing in a notably different arrangement from its metal counterpart.
Although the PVC instrument was designed to be an ensemble instrument it was soon discovered by various solo artists who saw the merits of the instrument for their musical purposes. The bore is wider than what one usually finds in a metal double contrabass flute. The instrument is comparatively light, weighing only 7 kg (compared to 15 kg for the brass version), and can be produced relatively quickly and inexpensively. In addition, the PVC appears to produce a broad tone.
...
Wikipedia