A flute was a musical instrument. It was one of several instruments which the Eighth Doctor could play. (PROSE: The Year of Intelligent Tigers)
Jo Grant incorrectly called the Second Doctor's recorder a flute when it appeared on the Third Doctor's TARDIS console. (TV: The Three Doctors) A confused Sixth Doctor made a similar mistake, while suffering from a time-slip with the Second Doctor. (TV: The Two Doctors)
The Fourth Doctor played out Bach's Badinerie, Orchestral Suite No. 2 in B minor on his reed flute. (TV: The Power of Kroll) The Fifth Doctor could not play the flute. (AUDIO: Tartarus) The Seventh Doctor knew how to play the flue, but forgot how after an encounter with Sandy. (AUDIO: The Dread of Night)
On an Earth-like planet, the Second Doctor played a note on his flute which activated a magnet in the TARDIS. This attracted the belts the fair-haired people of that world were wearing, thus enabling them to pass the second of the tests of Trefus. (COMIC: The Tests of Trefus)
A lassimater was part flute, part recorder and part didgeridoo, and made the most beautiful music in the universe. (PROSE: Most Beautiful Music)