The saxophone consists of an approximately conical tube of thin metal, most commonly brass, flared at the tip to form a bell. At intervals along the tube are between 20 and 23 tone holes of varying size, including two very small ‘speaker’ holes to assist the playing of the upper register.
These holes are covered by pads which are capable of pressing the holes
to produce an airtight seal; at rest some of the holes stand open and
others are closed by pads. The pads can be controlled by a number of
keys by the left and right fingers, while the left thumb operates an octave key to open the speaker holes for the upper register. The fingering for the saxophone is a combination of that of the oboe with the Boehm system, and is very similar to the flute or the upper register of the clarinet. On the larger instruments, the
leverage required to play the very lowest notes (which are customarily
played with the left and right little fingers) is great enough that additional keywork is introduced to enable these to be played with the thumbs.

The simplest design of saxophone is a straight conical tube, and the sopranino and soprano saxophones are usually of this straight design. However, as the
lower-pitched instruments would be unacceptably lengthy if straight,
the larger instruments usually incorporate a U-bend at or slightly
above the third-lowest tone hole. As this would cause the bell of the
instrument to point almost directly upwards, the end of the instrument
is either beveled or tilted slightly forwards. This U-shape has become
an iconic feature of the saxophone family, to the extent that soprano and even
sopranino saxes are sometimes made in the curved style even though this
is not strictly necessary. By contrast, tenors and even baritones have occasionally been made in the straight style. Most commonly, however, the alto and tenor saxophones incorporate a curved ‘crook’ above the highest
tone hole but below the top speaker hole, tilting the mouthpiece
through 90 degrees; the baritone, bass and contrabass extend the length
of the bore mainly by double-folding this section.