Microtones are musical intervals smaller than a semitone, the smallest step on a standard piano keyboard. In Western music, an octave is divided into 12 equal semitones, each worth 100 cents (a unit used to measure pitch differences). Any interval smaller than 100 cents qualifies as a microtone. These tiny pitch differences might sound exotic to ears trained on pianos and guitars, but they’re fundamental to many of the world’s oldest musical traditions and increasingly common in contemporary Western music.
How Musical Pitch Is Measured
To understand microtones, it helps to know how musicians measure the distance between notes. The standard unit is the cent, and there are 1,200 cents in one octave. In the 12-tone equal temperament system used across most Western music, each semitone (say, from A to B-flat) spans exactly 100 cents. The frequency ratio between any two adjacent notes is approximately 1.05946:1.
This system is a compromise. It spaces all 12 notes equally so that music sounds acceptable in every key, but it slightly distorts the natural harmonic relationships between notes. A perfectly tuned major third, based on the physics of vibrating strings, sits at about 386 cents. In equal temperament, that same interval is 400 cents, roughly 14 cents sharp. Most listeners never notice, but trained ears can hear the difference, and entire musical cultures have built their sound around those in-between pitches.
Microtones in Arabic and Indian Music
Many non-Western musical systems treat microtones not as exotic additions but as core building blocks. Arabic maqam music uses intervals of approximately 150 cents, often called three-quarter tones. In the maqam Bayati, for example, the second note of the scale (called Sikah) is an “E half flat,” sitting 150 cents above D and 150 cents below F, exactly midway between two notes that a piano could play. These measurements are approximations; skilled performers shade these pitches subtly depending on the emotional character of the piece.
Indian classical music goes even further. Its system divides the octave into 22 shrutis, or microtonal pitch positions, each serving a specific melodic and emotional function within different ragas. This concept was first described in Bharata’s Natya Shastra, a treatise dating to roughly 200 BCE to 200 CE. Rather than fixed steps on a keyboard, shrutis act more like precise targets that performers reach through subtle vocal slides or string bends. Each raga has its own set of permissible shrutis and rules governing which pitches can follow which, creating an expressive vocabulary that 12-tone equal temperament simply cannot reproduce.
Why Western Tuning Leaves Gaps
The 12-tone system became dominant in the West largely for practical reasons: it lets keyboards, fretted instruments, and orchestras play together in any key without retuning. But this convenience comes at a cost. Several naturally occurring harmonic intervals fall between the cracks of 12 equal steps.
One example is the harmonic seventh, a naturally occurring interval that’s noticeably flatter than the minor seventh on a piano. In 12-tone equal temperament, the closest available note is so sharp that the harmonic seventh effectively doesn’t exist in the system. Another gap involves the neutral third, an interval exactly halfway between a minor third and a major third. Because the perfect fifth in 12-tone tuning spans seven semitones (an odd number), it can’t be split evenly in half, making a true neutral third impossible to play.
These gaps aren’t just theoretical curiosities. They represent sounds that human ears find consonant and emotionally resonant, sounds that other musical cultures use freely but that Western instruments were designed to skip over.
Alternative Tuning Systems
Composers and theorists have developed tuning systems that reclaim these lost intervals. One approach is just intonation, which tunes notes to exact whole-number frequency ratios rather than the equal divisions of the octave. A just-tuned fifth is only about 2 cents flat compared to equal temperament, barely noticeable. But a just-tuned major third is nearly 14 cents flatter than its equal-tempered version, a difference that gives chords a strikingly pure, beatless quality.
Another approach divides the octave into more than 12 equal steps. A 31-tone equal temperament, for instance, produces a major third that’s less than 1 cent away from a perfectly tuned one (compared to almost 14 cents off in standard tuning). It also provides close approximations of the harmonic seventh and the neutral third, and it creates a closed circle of fifths, meaning you can modulate through all keys and return to where you started. Other systems use 19, 22, or even 53 equal divisions, each offering different tradeoffs between harmonic purity and practical playability.
Harry Partch’s 43-Tone System
The American composer Harry Partch took the most radical approach of the 20th century, building a 43-tone-per-octave scale based on just intonation. His system used harmonic ratios involving the integers 4, 5, 6, 7, 9, and 11, reaching well beyond the resources of conventional tuning. Because no existing instruments could play his music, Partch spent his life building sculptural custom instruments and composing theatrical works for them.
Ben Johnston’s String Quartets
Composer Ben Johnston developed a notation system for what he called Extended Just Intonation, designed so that standard acoustic instruments (particularly string quartets) could perform microtonal music. His system uses “+” and “-” symbols to raise or lower a pitch by a syntonic comma, roughly 22 cents, just over a fifth of a semitone. Additional symbols based on prime numbers indicate other microtonal adjustments. His String Quartet No. 7, composed in 1984, moves through a scale of 176 distinct pitches. Johnston’s work demonstrates that microtonal music doesn’t require electronic instruments or exotic hardware; four skilled string players with precise intonation can navigate extraordinarily complex pitch landscapes.
Playing Microtones on Physical Instruments
Fretless instruments like violins, cellos, trombones, and the human voice can produce microtones naturally. The player simply adjusts their finger position or embouchure to land between standard pitches. Fretted instruments are trickier, but guitarists have found solutions. Luthiers have built guitars with additional frets for 19-tone, 22-tone, 31-tone, quarter-tone, and 17-tone equal temperaments. Building a refretted guitar is surprisingly accessible; even a first attempt on an inexpensive electric guitar can produce a reasonably accurate 31-tone instrument.
Fretless bass guitars offer another option. Instead of installing new frets, players mark microtonal positions along the side of the neck as visual guides. Slide guitars take a different approach entirely, using painted or engraved fret guides rather than raised frets, which allows players to work with highly complex systems like 53-tone equal temperament or just intonation ratios.
Microtones in Digital Music Production
Software has made microtonal music far more accessible than it was in Partch’s era. Scala, the most widely used microtonal software tool, lets users create, edit, compare, and store tuning systems. You can enter intervals as frequency ratios or cent values, mix both within a single scale, and export tuning data to hardware synthesizers or software instruments.
Scala uses its own scale file format that has become a de facto standard. Dozens of software synthesizers accept Scala files directly for retuning, bypassing the need for complex MIDI workarounds. For instruments that don’t support the format natively, Scala can generate MIDI files that apply microtonal tuning through pitch bend commands or the MIDI Tuning Standard, a protocol that allows real-time single-note pitch adjustments. This means producers working in any digital audio workstation can experiment with microtonal scales without specialized hardware.
The practical result is that a bedroom producer today has access to tuning possibilities that would have required a workshop full of custom-built instruments just a few decades ago. Whether you’re exploring Arabic maqam intervals, replicating Indian shruti positions, or inventing entirely new scales, the tools exist to hear and record the results immediately.