Semitones and Cents Explained
The units behind every pitch shift, transposition, and tuner.
What a semitone is
A semitone is the smallest interval in Western music — the distance between two adjacent piano keys, or two adjacent frets on a guitar. There are 12 semitones in an octave. The chromatic scale (C, C#, D, D#, E, F, F#, G, G#, A, A#, B, C) is all 12 semitones in order. When loope asks you to transpose by semitones, each increment is one step up or down the piano keyboard. +12 semitones = up one octave. -12 = down one octave.
What a cent is
A cent is 1/100 of a semitone. There are 1200 cents in an octave. Cents measure small pitch deviations that are finer than 'is this note C or C#'. An electronic tuner reading +5 cents means your note is 5/100 of a semitone sharper than the target. Cents are what separate 'perfect tuning' from 'out of tune': humans can hear differences as small as 5–10 cents, and professional musicians aim to stay within ±5 cents.
Why 12 divisions aren't equal mathematically
The 12-semitone division of the octave is called 'equal temperament' because each semitone is the same multiplicative factor — about 1.0595 (the twelfth root of 2). Doubling a frequency gives an octave; multiplying 12 times by 1.0595 also gives 2x, so 12 semitones covers one octave. This makes transposition work cleanly: +1 semitone = multiply frequency by 1.0595. +2 semitones = multiply by 1.0595 twice. Et cetera.
How loope uses these units
loope's transpose control is expressed in semitones, so +1 moves every note up by one semitone (one fret on guitar, one key on piano). For fine-tuning — say, matching a recording that's slightly out of standard A440 tuning — cents would be useful. Most music practice happens at the semitone level; cents matter mainly for session musicians matching reference recordings or working with ensembles tuned to A441 or A442.
Transpose in semitones in loopeQuick reference for common intervals
Minor second: 1 semitone. Major second: 2 semitones. Minor third: 3 semitones. Major third: 4 semitones. Perfect fourth: 5 semitones. Tritone: 6 semitones. Perfect fifth: 7 semitones. Minor sixth: 8 semitones. Major sixth: 9 semitones. Minor seventh: 10 semitones. Major seventh: 11 semitones. Octave: 12 semitones. Memorizing these turns 'transpose up a fifth' into 'transpose up 7 semitones', which is a small but useful bit of fluency.
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Frequently Asked Questions
Yes. 'Semitone' and 'half-step' are interchangeable terms for the same interval.
A whole step is two semitones. A major second. The distance from C to D, or D to E.
Because Western music is based on the 12-semitone equal-tempered scale, and having a fret for each semitone lets you play any note in the scale on any string. Guitars in other tuning systems (e.g., Arabic oud) often have additional frets for quarter-tones.
Barely. Most humans can distinguish 5–10 cent pitch differences in isolation; in a musical context even 3–5 cents can be detected by trained ears. Below 1 cent is inaudible to almost everyone.
International agreement in the 20th century. Orchestras had used a range of pitches (A=435 to A=450) historically, and 440 was set as the reference in 1939 and formalized in 1955. Some orchestras still tune to A=442 or A=443 for a slightly brighter sound.