The octobass is a bowed string instrument that has an appearance similar to a double bass but with nearly double its size (with a length of approximately two meters) and tuned to one octave lower (extending down to a C below the normal range of human hearing). Owing to its extreme fingerboard length and string thickness, it is played by a musician standing on a stool and using a system of levers and pedals rather than with a conventional bow. Because of its great size and unwieldiness, only about five octobasses have ever been built, and extremely few compositions have been written that include them.