The tenor recorder is a member of the recorder family. It has the same form as a soprano (or descant) recorder and an alto (or treble) recorder, but it produces a lower sound than either; a still lower sound is produced by the bass recorder.
The tenor recorder, like the soprano recorder, is tuned in C, but an octave lower. Because of its larger size, many tenors have keys to make it easier to play the lowest C, C♯, D, and D♯.
In modern notation, the tenor is written at sounding pitch, unlike most of the other recorder sizes, which (except sometimes the alto) are written an octave lower than they sound (Lasocki 2001).
History
In German-speaking countries in the 18th century, the tenor recorder was named Quartflöte (fourth flute), after the interval it forms below the ordinary recorder (alto) in F. Confusingly, the same name was used for the soprano recorder in C, apparently because it forms the same interval above the alto in G. At the same time, the English and French equivalents, "fourth flute" and "flute du quatre", meant a recorder a fourth higher than the alto in F—that is, an instrument with B♭ as its lowest note (Lasocki 2001).