Microtonal music is a type of harmony, or organization of musical sounds, which uses intervals smaller than those typically played in western music. Western musical keys, or patterns of notes, are divided into half steps and whole steps. The half step is the smallest interval recognized by Western music. In microtonal music, intervals smaller than a half step are used.
There are 12 half steps in an octave in the Western style. Scales are made up of combinations of half steps and whole steps. Microtonal music has a much broader range of musical patterns, as smaller intervals are used, and the number of intervals per scale pattern is not standardized. Different musicians and composers use their own divisions, sometimes dividing the octave into 19 or 31 equal steps. In other cases, the octave is not the basis for the musical pattern at all.
Non-western cultures sometimes use microtones in their music. They may use instruments or the human voice to achieve the sound. Sometimes composers invent their own instruments or adapt existing instruments in order to play microtones.
Not all instruments are designed to play microtonal music. Western instruments usually are not, but some can be adapted for the purpose. Although it is possible for wind and brass players to adjust the pitch of their instruments in microtones through the use of air and mouth and finger placement, it is difficult to achieve accuracy. The exception to this is the trombone, which uses a slide to change the length of the tubes to change the pitch of the sound. Trumpet, tuba, and horn could not be adapted as easily.
String instruments that are not fretted are also capable of playing microtonal music, and upright bass, violin, viola, cello, and many other stringed instruments are often used to this kind of music. In some cases, it is hard for a musician with large fingers to achieve the correct position on the instrument, as the microtones are extremely close together on the neck of the instrument.
Wind instruments, like the clarinet, flute, and saxophone, are not constructed to play microtones. A wind instrument has holes placed at intervals along a wooden or metal tube. The holes are closed to adjust pitch. Although covering half of a hole will change the pitch less than a half step, the mechanism on wind instruments prevents this method from being used.
Even if an instrument can play microtones, it still takes a well trained musician to perform the music. Microntonal music requires a very refined sense of hearing to distinguish between tones. It would be difficult for a musician who has been trained to play music in the twelve note octave pattern to learn to play microtonal music because his ear would be unaccustomed to the tuning.