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.