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 28 June 1846. The patent encompassed 14 versions of the fundamental design, split into two categories of seven instruments each, and ranging from sopranino to contrabass. A limited number of instruments in the series pitched in F and C were produced by Sax, but the series pitched in E and B quickly became the standard. All the instruments were given an initial written range from the B below the treble staff to the E one half-step below the third ledger line above staff, giving each saxophone a range of two and a half octaves. Sax's patent expired in 1866. Thereafter, numerous other instrument manufacturers implemented their own improvements to the design and keywork. 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 certain legato passages and wide intervals extremely difficult to finger; that system would later evolve with extra keys, linkage mechanisms, and alternate fingerings to make some intervals less difficult. Early in the development of the saxophone the upper keyed range was extended to E, then F above the staff; 1880s era sheet music for saxophone was written for the range of low B to F. In 1887 the Buffet-Crampon company obtained a patent for extending the bell and adding an extra key to extend the range downwards by one semitone to B. This extension is standard in modern designs, with the notable exception of baritone saxophones keyed to low A. The upper range to F would remain the standard for nearly a century until a high F key became common on modern saxophones. In the 1840s and 1850s, Sax's invention gained use in small classical ensembles (both all-saxophone and mixed), as a solo instrument, and in French and British military bands. Saxophone method books were published and saxophone instruction was offered at conservatories in France, Switzerland,