Consider the piano-forte. When introduced in 1727, in order for its sound to be compatible with that of the harpsichord, it had a produce a very bright sound, using hard hammers. Later, felt hammers were used to soften the sound, which had the effect of minimizing the energy going into the higher harmonics (e.g., the 7th, 11th, and 13th). These partials are those which clash worst in 12-tone equal temperament; dulling them accelerated the move away from the harpsichord’s 1/n-comma meantone (and various well-temperaments) to 12-tone equal temperament. It is not a coincidence that felted hammers became the norm in the mid-1800’s, when 12-tone equal temperament was becoming the norm, too.

Likewise, the development of the valves for brass instruments in the early 1800’s enabled them to play chromatically for the first time, rather than just playing the harmonics of a fundamental, as bugles do. These valves were also perfected in the mid-1800’s, facilitating the rise of equal temperament.

The Boehm System of fingering mechanisms was also designed specifically with 12-tone equal temperament in mind.

A counter-example are the free-reed instruments (concertinas and accordions), which produce a timbre which clashes with equal temperament (often producing harsh combination tones). The accordion in particular outsold the guitar (all types) in the USA by 5:1 as recently as 1953, but the amplification of the acoustic guitar and the emergence of the electric guitar out-competed the accordion for the niche of loud, polyphonic dance-band instruments, in part due to the guitar’s harmonic sound.

Jazz can be described in part as the extension of tonal theory to embrace the 7th harmonic, which had been largely ignored by European music theorists. As described above, Western instruments had been re-designed in the mid-1800’s to fit 12-tone equal temperament, in part by dulling the 7th partial. Jazz therefore favored those instruments which enabled flexible intonation, of which the saxophone is the archetype.

Today, technical innovations such as waveguide synthesis are languishing due to the lack of a sufficiently-expressive controller. Thumtronics’ Thummer offers a significant leap in expressive power, ease of learning, and creative freedom (through Dynamic Tuning).

Look to Second Life.