Most Western musical instruments adhere to the 12-note (12-tone) and octave system, which forms the foundation of Western music theory.
However, some instruments or systems deviate from this standard, either because they predate the system or serve specialised functions.
Here's an overview of the Western instruments and contexts that don't strictly follow the 12-note/octave system and the reasons why:
1. Tuned percussion (e.g., timpani, gongs)
Reason:
Tuned percussion instruments such as the timpani are capable of producing specific pitches, but they are often limited to a narrow range (like a few notes rather than a full 12-note scale).
Instruments like gongs and chimes may produce more complex overtones and inharmonic partials that don’t conform to the 12-tone equal temperament system.
Their sounds are rich and more “noise-like,” which makes them useful for special effects, but not for producing a series of discrete pitches in the standard system.
2. Fretless string instruments (e.g., violin, cello)
Reason:
Instruments like the violin, cello, and other fretless string instruments are not inherently bound to the 12-note system because players can produce microtones (notes between the 12 standard pitches).
While they often perform music based on the 12-note octave system, these instruments have the flexibility to perform microtonal or non-Western music that uses different tuning systems.
3. Early music instruments (e.g., natural trumpet, cornett)
Reason:
Before the adoption of 12-tone equal temperament in the 17th and 18th centuries, many early Western instruments used just intonation or meantone temperament, which resulted in slightly different intervals than the modern 12-tone system.
Instruments like the natural trumpet (which only plays harmonics) and cornett were tuned according to these systems and did not always follow the even spacing of notes across an octave that we use today.
4. Bagpipes
Reason:
Some Western bagpipes, like the Scottish Great Highland Bagpipe, use a scale that doesn’t fit into the 12-tone equal temperament system.
They are tuned according to a just intonation system, which emphasises natural harmonic relationships, resulting in intervals that differ slightly from the 12-tone system.
5. Harmonics on string instruments
Reason:
Harmonic overtones produced on string instruments (like a violin or guitar) do not conform exactly to the 12-note system.
The natural harmonic series results in frequencies that deviate from the equal-tempered scale, especially in higher partials. For example, the 7th harmonic is flatter than its equal-tempered equivalent.
6. Experimental or microtonal instruments
Reason:
Some modern instruments, such as microtonal pianos or specially designed guitars with extra frets, are deliberately built to explore music outside of the standard 12-tone system.
These instruments may divide the octave into more than 12 pitches (e.g., 24, 31, or 53 divisions) for microtonal music.
Composers like Harry Partch designed and built their own instruments to play music in alternative tuning systems.
7. Early keyboard instruments (e.g., clavichord, harpsichord)
Reason:
In earlier centuries, keyboard instruments like the clavichord or harpsichord were tuned according to non-equal temperaments, such as Pythagorean tuning or meantone temperament.
These systems created pure intervals (especially for thirds and fifths) in some keys but made other keys sound more dissonant.
The idea of a fully chromatic, equally spaced 12-note system developed gradually and wasn’t uniformly applied until well into the Baroque period.
8. Non-12-TET brass instruments (natural horn, trombone)
Reason:
Like the natural trumpet, the natural horn produces a series of harmonic overtones that do not fit neatly into the 12-tone system, particularly in the lower registers.
Even instruments like the trombone, with its glissando (sliding) capability, can produce pitches between the notes of the standard 12-tone system, giving it the flexibility to perform microtonal music.
Why Do Some Instruments Not Follow the 12-Note System?
The 12-tone equal temperament (12-TET) system developed over centuries to address the need for instruments that could play equally well in all keys, a necessity for the increasing complexity and modulations in Western music.
However, there are several reasons why some instruments don’t fully conform to this system:
Historical evolution: Instruments like the natural trumpet or early harpsichords evolved before the 12-tone system was standardised.
Harmonic complexity: Instruments like gongs, timpani, or even string harmonics produce complex overtones that can’t be perfectly mapped to a 12-tone scale.
Cultural specificity: Instruments like certain bagpipes are tied to folk traditions that use different tuning systems, like just intonation or Pythagorean tuning.
Flexibility: Fretless string instruments, trombones, and others allow players to perform microtones, creating music outside the confines of the 12-tone system when desired.
Experimental music: Contemporary composers and musicians have designed instruments and systems that intentionally go beyond the 12-tone scale, exploring microtonality and other tuning systems.
