The tenor bassoon or tenoroon is like the alto bassoon in that it is an old instrument that has recently been revived. The tenor size of bassoon first began to appear during the 19th century but was not widely used as the real need at the time was for a working contrabassoon (and not the sarrusophone that was currently in use). 

Modern instruments come in two flavours; F and G.  The F instrument (also known as a quart-bassoon) is pitched a fourth higher than the bassoon, while the G instrument (also known as a quint-bassoon) is pitched a fifth above the bassoon.  Soundwise, there is very little difference between the two: in general, professional players prefer the F instrument, while the G instrument is more suitable for children.

Unlike the alto bassoon, the tenor bassoon is fully chromatic.  However, its range is only 3 octaves, so its top note is exactly the same as on the standard bassoon.