Fundamentals

What a Semitone Is

A semitone, also called a half step, is the smallest interval used in standard Western tuning: the gap between any note and the very next one, white key or black. In 12-tone equal temperament (12-TET), the tuning system nearly all modern instruments and DJ software use, each semitone raises frequency by a fixed ratio of 2^(1/12) ≈ 1.0595, and a semitone is worth exactly 100 cents, the finer unit used for tuning precision. Twelve semitones stack to one octave, doubling the frequency exactly.

Reference

Semitones to Interval Names

Every interval in Western music theory maps to a fixed number of semitones, regardless of which notes it starts from:

Why it matters

Why DJs Care About Semitones

Every pitch shift is a semitone shift. Nudge a pitch fader or key-lock control and the track's key moves by whole or fractional semitones, on most DJ software and hardware roughly 6% of tempo change per full semitone, though the exact figure varies by gear. That means a big tempo change to bridge two tracks can quietly clash their keys unless you check the resulting shift. The key & BPM changer and pitch & tempo calculator work out the exact semitone shift for a given percentage change, so you know before you commit to the transition.

One important gotcha for harmonic mixing: semitones and Camelot numbers do not move in lockstep. +1 semitone equals +7 positions on the Camelot wheel (mod 12), following the circle of fifths rather than a straight chromatic count. To convert a semitone shift directly into Camelot terms, use the key transposer or the interactive Camelot wheel.

Frequently Asked Questions