controlled by opening or closing the tone holes along the body of the instrument to change the length of the vibrating air column. The tone holes are closed by leather pads connected to keys—most are operated by the player's fingers, but some are operated using the palm or the side of a finger. There is an octave key, which raises the pitch of the lower notes by one octave. The lowest possible note, with all of the pads closed, is the (written) B below middle C. Modern baritone saxophones are commonly constructed to play a low A, and a small number of altos keyed to low A have also been manufactured. The highest keyed note has traditionally been the F two and a half octaves above the low B, but higher-quality instruments now have an extra key for a high F, and a high G key can be found on some modern soprano saxophones. Notes above the keyed range are part of the altissimo register of the saxophone and can be produced using advanced embouchure techniques and fingering combinations. Saxophone music is written in treble clef (appropriately transposed for each different type of instrument) and all saxophones use the same key arrangement and fingerings, enabling players to switch between different types of saxophones fairly easily. Soprano and sopranino saxophones are usually constructed with a straight tube with a flared bell at the end, although some are made in the curved shape of the other saxophones. Alto and larger saxophones have a detachable curved neck and a U-shaped bend (the bow) that directs the tubing upward as it approaches the bell. There are rare examples of alto, tenor, and baritone saxophones with mostly straight bodies. The baritone, bass, and contrabass saxophones accommodate the length of the bore with extra bends in the tube. The fingering system for the saxophone is similar to the systems used for the oboe, the Boehm-system clarinet, and the flute. Materials From the earliest days of the saxophone the body and key cups have been made from sheet brass stock, which can be worked into complex shapes. The keywork is manufactured from other types of brass stock. King made saxophones with necks and bells of sterling silver from the 1930s into the early 1960s. Yanagisawa revived this idea in the 1980s and later introduced instruments entirely made of sterling silver. Keilwerth and P. Mauriat have used nickel