The saxophone was designed in 1846 by Adolphe Sax, a Belgian instrument maker, flautist, and clarinetist. Born in Dinant and originally based in Brussels, he moved to Paris in 1842 to establish his musical instrument business. Before working on the saxophone, he made several improvements to the bass clarinet by improving its keywork and acoustics and extending its lower range. Sax was also a maker of the ophicleide, a large conical brass instrument in the bass register with keys similar to a woodwind instrument. His experience with these two instruments allowed him to develop the skills and technologies needed to make the first saxophones.
As an outgrowth of his work improving the bass clarinet, Sax began developing an instrument with the projection of a brass instrument and the agility of a woodwind. He wanted it to overblow at the octave, unlike the clarinet, which rises in pitch by a twelfth when overblown. An instrument that overblows at the octave has identical fingering for both registers.
Sax created an instrument with a single-reed mouthpiece and conical brass body. Having constructed saxophones in several sizes in the early 1840s, Sax applied for, and received, a 15-year patent for the instrument on June 28, 1846. The patent encompassed 14 versions of the fundamental design, split into two categories of seven instruments each, and ranging from sopranino to contrabass.
Although the instruments transposed at either F or C have been considered "orchestral", there is no evidence that Sax intended this. As only three percent of Sax's surviving production were pitched in F and C, and as contemporary composers used the E♭ alto and B♭ bass saxophone freely in orchestral music, it is almost certain that Sax experimented to find the most suitable keys for these instruments, settling upon instruments alternating between E♭ and B♭ rather than those pitched in F or C, for reasons of tone and economy (the saxophones were the most expensive wind instruments of their day). The C soprano saxophone was the only instrument to sound at concert pitch. All the instruments were given an initial written range from the B below the treble staff to the F, one space above the three ledger lines above staff, giving each saxophone a range of two and a half octaves.
Sax's patent expired in 1866. Thereafter, numerous saxophonists and instrument manufacturers implemented their own improvements to the design and keywork.
The first substantial modification was made by a French manufacturer who extended the bell slightly and added an extra key to extend the range downwards by one semitone to B♭. It is suspected that Sax himself may have attempted this modification. This extension is currently standard in almost all modern designs, along with other minor changes such as added keys for alternate fingerings. Using alternate fingerings allows better fluency on the instrument. Alternate fingerings are often used for trilling, difficult musical passages, and interval jumps.
Sax's original keywork, which was based on the Triebert system 3 oboe for the left hand and the Boehm clarinet for the right, was simplistic and made playing certain legato passages and wide intervals extremely difficult to finger, so numerous developers added extra keys and alternate fingerings to make chromatic playing less difficult.
While early saxophones had two separate octave vents to assist in the playing of the upper registers (just as modern instruments do), Sax's original design had two separate octave keys operated by the left thumb. A substantial advancement in saxophone keywork was the development of a method by which the left thumb operates both tone holes with a single octave key, which is now universal on modern saxophones.
The modern layout of the saxophone emerged during the 1930s and 1940s, first with right-side bell keys introduced by C. G. Conn on baritones, then by King on altos and tenors. The mechanics of the left hand cluster were revolutionized by Selmer with their balanced action instruments in 1936 and in 1948, when Selmer introduced their Super Action saxophones with offset left and right hand stack keys. Between 30 and 40 years after Selmer devised their final layout it had been adopted for virtually every saxophone being produced, from student to professional models.
One of the most radical, however temporary, revisions of saxophone keywork was made in the 1950s by M. Houvenaghel of Paris, who completely redeveloped the mechanics of the system to allow a number of notes (C♯, B, A, G, F and E♭) to be flattened by a semitone simply by pressing the right middle finger. This enables a chromatic scale to be played over two octaves simply by playing the diatonic scale combined with alternately raising and lowering this one digit. However, this keywork never gained much popularity, and is no longer in use.