form a bell, while the narrower end is connected to a single reed mouthpiece similar to that of the clarinet. At intervals down the bore are placed between 20 and 23 tone holes; these are covered by pads which can be pressed onto the holes to form an airtight seal. There are also two small speaker holes which, when opened, disrupt the lower harmonics of the instrument and cause it to overblow into an upper register. The pads are controlled by pressing a number of keys with the fingers of the left and right hands; the left thumb controls an octave key which opens one or other of the speaker holes. The original design of tenor saxophone had a separate octave key for each speaker hole, in the manner of the bassoon; the mechanism by which the correct speaker hole is selected based on the fingering of the left hand (specifically the left ring finger) was developed soon after Sax's patent expired in 1866. Although a handful of novelty tenors have been constructed 'straight', like the smaller members of the saxophone family, the unwieldy length of the straight configuration means that almost all tenor saxophones feature a 'U-bend' above the third-lowest tone hole which is characteristic of the saxophone family. The tenor saxophone is also curved at the top, above the highest tone-hole but below the highest speaker hole. While the alto is usually bent only through 80–90° to make the mouthpiece fit more easily in the mouth, the tenor is usually bent a little more in this section, incorporating a slight S-bend. The mouthpiece of the tenor saxophone is very similar to that of the clarinet: an approximately wedge-shaped tube, open along one face and covered in use by a thin strip of material prepared from the stem of the giant cane (Arundo donax) commonly known as a reed. The reed is shaved to come to an extremely thin point, and is clamped over the mouthpiece by the use of a ligature. When air is blown through the mouthpiece, the reed vibrates and generates the acoustic resonances required to produce a sound from the instrument. The mouthpiece is the area of the saxophone with the greatest flexibility in shape and style, so the timbre of the instrument is primarily determined by the dimensions of its mouthpiece. The design of the mouthpiece and reed play a big role in how