Microtonality is not a genre, or a technique, or a style. It has as many interpretations, modes of expression, and techniques as tonal music. In order to understand microtonal principles, we must first distinguish the multitude of perspectives that microtonal composition can take.

Composers interested in intonation systems other than the standard equal-tempered one practiced in the Western Classical tradition, particularly numerous Americans composers, including Harry Partch (1901-74), Benjamin Johnston (b. 1926), LaMonte Young (b. 1935), and Kyle Gann (b. 1955), seek to utilize the more scientifically accurate acoustical relationship between pitches based on the natural harmonic series.

Others, such as the Mexican composer Julián Carrillo (1875-1965) and the Czech, Alois Hába (1893-1973), initially began their work by subdividing the equal-tempered scale (based on 12 semi-tones) proportionally into quarter-, third-, eighth-tones, or even finer gradations. These scales (with 24 steps if quarter-tone, or 48 if eighth-tone) are then applied to largely traditional forms, with the extended interval palette enhancing expressive subtleties of melodic and harmonic configurations. Carrillo’s work culminated in his full length, quarter-tone Mass, while Hába’s opera, The Mother (also in quarter-tones) is perhaps the most exhaustive implementation of a microtonal harmonic system of its type in the literature.

The quintessential American maverick composer, Charles Ives (1874-1954), first explored the possibilities of microtones in a holistic fashion in his Three Quarter-Tone Pieces for Two Pianos. In this case, the two performers play on pianos that are equal-tempered, but a quarter-tone apart from one another. Therefore, in order to achieve an integrated melodic and harmonic conception for the compositions, the two performers and instruments had to be conceived as if one. When he scored this work he avoided any need for a particular microtonal notation: in effect the part for the pianist with the re-tuned instrument is similar to tablature since the microtones are not indicated, but sound when the correct keys are depressed. John Eaton (b. 1935) found another solution with his Microtonal Fantasy: scored for one performer, two pianos are placed at ninety-degree angles to one another (and tuned a quarter-tone apart) so that they could be played simultaneously. Others working with pianos (including the aforementioned Carrillo) have experimented with stacking keyboards, altering the layout of the keyboard, or changing the pitch designation of the individual keys within the octave.

Another American, Ezra Sims (b. 1928), is notable for his amalgamation of both of these significant trends into a personal mode of expression for which he developed an exhaustive, and complicated, notational scheme, which has since been adopted by numerous composers in his region (New England). The history of notating microtonal music has been one replete with idiosyncrasies. As long as such a plurality of approaches persists, the task of finding one all-encompassing method may well elude theorists and composers alike. However, student composers should try to discover an established notation to suit their needs rather than invent one that is redundant; the less unfamiliar symbols needed in a composition, the better chance the piece has for interpretation by performers.

Iannis Xenakis (1922-2001) and Giacinto Scelsi (1905-1988) used microtones to supplement their pitch resources, especially when creating subtle variations in the harmonic ‘beatings’ that result between two very close parts. Xenakis’ Nomos Alpha, for solo cello, is an excellent example of this: in the score he instructs the performer to perform specific (and quickly changing) beating patterns between two conjunct strings. Scelsi’s music, in broad terms, is organized around individual pitches and the drama that can be created by the manipulation of their interaction with a ‘halo’ of micro-intervals that surround them. His quasi-concerto for violin and orchestra, Anahit, calls for the soloist to prepare his/her instrument with a precise scordatura re-tuning to enable the finest degree of microtones.

Still other composers use microtones simply as an ornamental feature to their work. This can include pitch bends, neighboring tones, or similar devices that don’t use microintervals as the primary substance of the composition. Often this is also found in ethnic and folk music of the world.

All non-percussive instruments (with the exception of the tympani) of the standard orchestra have the ability to play the microtonal gradations in pitch with varying degrees of facility. Each has its own inherent technique (or combination of techniques) to achieve the accurate intonations desired. Wind instruments combine embouchure changes with altered key fingerings, while the strings need only correct digit placement on the fingerboard. Harry Partch built his own orchestra (primarily consisting of percussion instruments) in accordance with his intonation system with no other solution available to make possible the performance of his visionary concepts.