airstream using the diaphragm and vocal tract. Fingers The finger holes, used in combination or partially covered, affect the sounding pitch of the instrument. At the most basic level, the sequential uncovering of finger holes increases the sounding pitch of the instrument by decreasing the effective sounding length of the instrument, and vice versa for the sequential covering of holes. In the fingering 01234567, only the bell of the instrument is open, resulting in a low pressure node at the bell end of the instrument. The fingering 0123456 sounds at a higher pitch because the seventh hole and the bell both release air, creating a low pressure node at the seventh hole. Besides sequential uncovering, recorders can use forked fingering to produce tones other than those produced by simple sequential lifting of fingers. In the fingering 0123, air leaks from the open holes 4,5,6, and 7. The pressure inside the bore is higher at the fourth hole than at the fifth, and decreases further at the 6th and 7th holes. Consequently, the most air leaks from the fourth hole and the least air leaks from the seventh hole. As a result, covering the fourth hole affects the pitch more than covering any of the holes below it. Thus, at the same air pressure, the fingering 01235 produces a pitch between 0123 and 01234. Forked fingerings allow recorder players to obtain fine gradations in pitch and timbre. A recorder's pitch is also affected by the partial covering of holes. This technique is an important tool for intonation, and is related to the fixed process of tuning a recorder, which involves the adjustment of the size and shape of the finger holes through carving and the application of wax. One essential use of partial covering is in "leaking," or partially covering, the thumb hole to destabilise low harmonics. This allows higher harmonics to sound at lower air pressures than by over-blowing alone, as on simple whistles. The player may also leak other holes to destabilise lower harmonics in place of the thumb hole (hole 0). This technique is demonstrated in the fingering tables of Ganassi's Fontegara (1535), which illustrate the simultaneous leaking of holes 0, 2, and 5 to produce some high notes. For example, Ganassi's table produces the 15th (third octave tonic) as the fourth harmonic of the tonic, leaking holes 0, 2 and 5 and produces the 16th as the