The reed contrabass in C, otherwise known as the Italian: contrabbasso ad ancia or French: contrabasse à anche, is a type of woodwind instrument. It is reminiscent of an ophicleide in appearance but, unlike the ophicleide, employs a double reed (akin to that of an oboe or Bassoon) for the purpose of sound production. It was developed by the Belgian maker Mahillion in the 1860s based on a slightly earlier design by the Czech maker ?ervený.
The instrument is typically of metal construction, with a conical and unusually wide bore. This width allows each note to be produced by opening only one tone hole, whereas, in other woodwind instruments, several tone holes must be opened to produce most notes (for this reason, all keys but that for the lowest note remain normally closed). This property greatly simplifies the fingering of the instrument, in that no alternative fingerings for individual notes or trill keys are needed, nor exist. The lowest note that the reed contrabass may typically achieve is D1 (DD) - the lowest D on a standard grand piano.
Although obscure, the instrument may still be procured, on request, from the Italian instrument manufacturer Orsi. The reed contrabass is sometimes confused with the contrabass sarrusophone, to which it bears some superficial resemblance.