Why isn't 6% exactly one semitone?

A semitone is a frequency ratio of the 12th root of 2 (1.0595). That's a 5.95% change; 6% is the round number used in practice.

Does key lock hurt the sound?

With small tempo changes the difference is tiny. With large changes (±8% and more) you may hear artefacts on vocals and sharp sounds.

Is a ±8% pitch range enough?

For most sets, yes. If you need a wider range (±16%), remember the key will move more than one step on the wheel, or turn key lock on.

Pitch, Tempo & Key Lock: How Does the Key Shift When Tempo Changes?

01The 6% rule

On a turntable, or a player with key lock off, raising the pitch speeds the audio up and raises it by the same ratio. One semitone is a speed change of about 5.95%; in practice, remember 6%.

+6% ≈ one semitone up → 7 steps forward on the wheel (8A → 3A)
−6% ≈ one semitone down → 7 steps back on the wheel (8A → 1A)
+12% ≈ two semitones up → 2 steps forward on the wheel (8A → 10A)

Pitch values in between (e.g. 3%) put the sound between two keys: the track sounds out of tune and fits no key exactly. Do the maths instantly with the pitch to key calculator.

02What key lock (master tempo) does

With key lock on, the player keeps the pitch fixed while it changes the tempo. The track speeds up, but its key stays the same. To do this, the audio is stretched in time in real time (time-stretching).

The price is quality: at small changes (±3–4%) the difference is barely audible, but at large changes vocals can sound metallic and drum attacks soft. As a rule, keep key lock on when the tempo gap is big, but pick tracks that keep the gap small.

03When off, when on?

On: when you mix harmonically and change the tempo by more than a few percent. The tagged key stays valid.
Off: when you want the vinyl feel, or when the tempo change is tiny (±1–2%; the key moves by at most a third of a semitone, which most ears won't notice).
Deliberate use: turning key lock off and raising the pitch by exactly 6% moves a track up a semitone. You can use it to bring a clashing track into a compatible key.

04Half and double tempo

A 70 BPM hip-hop track sits on the same grid as a 140 BPM dubstep track: every beat of one is two beats of the other. Software sometimes detects half or double tempo, too. If a track's BPM looks odd, check double or half; you can count it yourself with the tap tempo on the BPM page.

05From BPM to milliseconds

To lock delay and reverb effects to a track you need the beat length: 60,000 ÷ BPM is one beat in milliseconds. At 128 BPM one beat is 468.75 ms and half a beat 234.4 ms. The BPM page has a table for every note value.

06A practical workflow

Analyse your tracks and write key and BPM into the tags (key and BPM finder).
Group the set by tempo range; within a group, with key lock on, the keys stay valid.
If you need a big tempo jump between groups, turn key lock off and check in the calculator where the pitch moves the key.

Pitch, tempo and key lock: how the key shifts when the tempo changes