How Many Semitones Does Changing BPM Shift? Calculating Playback Speed and DJ Pitch %

The playback speed ratio is “new BPM ÷ original BPM”

Any tempo-change calculation starts with the playback speed ratio, which is “new BPM ÷ original BPM”. To take a BPM 120 song to 128, that’s 128 ÷ 120 ≈ 1.0667×; to drop a BPM 100 song to 90, it’s 0.9×.

The number on a DJ deck’s pitch fader, or a DAW’s “tempo ±%”, is that ratio minus 1, times 100. A ratio of 1.0667 is +6.67%, and 0.9 is −10%.

How many semitones the pitch moves when it changes with speed

If you change tempo by changing a record’s speed, a tape’s speed, or moving a DJ player’s pitch fader with key lock off, the pitch changes too. This is called “varispeed”.

Pitch is determined by frequency, and going up an octave (12 semitones) doubles the frequency. One semitone is the 12th root of 2, about 1.0595×. In other words, raising playback speed by about 5.95% raises the pitch by one semitone. The formula for semitones from a speed ratio is “semitones = 12 × log₂(ratio)”.

Going the other way, to get the speed from a chosen number of semitones, use “ratio = 2 to the power of (semitones ÷ 12)”. Varispeeding a BPM 120 song up one semitone puts the tempo at about 127.14; two semitones up gives about 134.7, and one semitone down about 113.26.

Calculating how to match two tracks’ tempos as a DJ

In a DJ mix, you match the next track’s tempo to the one that’s playing before you blend. To go from a BPM 124 track into a BPM 128 track, set the next track’s pitch fader to +3.23%. Many CDJ and DJ controller pitch faders let you switch ranges such as ±6%, ±8%, ±10% and ±16%, and the narrower the range, the finer the adjustment.

1. 1

   Check both tracks’ BPMs

   Make sure your DJ software’s auto-detection hasn’t come out at double or half. If you’re unsure, measure by tapping (how to find a song’s BPM).

2. 2

   Calculate the pitch fader percentage

   It’s “(target BPM ÷ next track’s BPM − 1) × 100”. BPM 124 → 128 is +3.23%, and 130 → 128 is −1.54%.

3. 3

   For big gaps, think in halves and doubles

   To go from BPM 87 hip-hop into BPM 174 drum and bass, treat 87 as double, 174, and you can blend without touching the pitch.

4. 4

   Decide whether to use key lock (master tempo)

   For large changes beyond about ±3%, the pitch change becomes noticeable with key lock off. Key lock on preserves the pitch, but the bigger the change, the more the sound quality may degrade a little.

If you match tempo without key lock, the two tracks’ keys shift too. BPM 124 → 128 raises the pitch about +0.55 semitones, for example, so two tracks that started in the same key can end up about half a semitone apart and sound sour. When harmonic mixing (blending with keys that work together), factoring in the semitone shift from the tempo change helps avoid clashes.

How this differs from changing tempo without changing key

Modern DAWs, playback apps and video sites’ speed controls mostly use a process called time-stretching, which changes only the tempo while keeping the key. The reverse, changing only the key while keeping the tempo, is pitch-shifting. Which one you use decides whether you need the semitone calculation at all.

• To practice an instrument at 0.75×, choose playback that keeps the key, or the pitch drops about 5 semitones and your tuning won’t match
• The bigger the time-stretch, the more likely attacks smear and vocals warble. Up to about ±10% it’s hard to notice
• Nightcore-style edits that change pitch and tempo together deliberately use varispeed (1.2–1.3× raises the pitch about 3–4.5 semitones)
• To change only the key so a song is easier to sing, see how to transpose chords for changing the chords

Using this with loops and transcribing by ear

To drop a drum loop made at BPM 120 into a BPM 128 project, time-stretching keeps the key, but changing the playback speed in a sampler raises it about +1.12 semitones. With material that has little sense of pitch, like drums, that often doesn’t matter, but loops with bass or chords will clash with the other parts. If you don’t know a loop’s BPM, work it out first with finding BPM from a loop’s length and number of bars.

When transcribing by ear, recordings taken from old vinyl or cassettes sometimes play back slightly faster (or slower) than the original performance, leaving the key somewhere between semitones. If a guitar tuned with a tuner just won’t match the recording, suspect that its playback speed is a few percent off, and correcting the pitch in steps of 0.1 semitone will make it easier to play along.

Guide values for slowing down to practice

When practicing a fast passage, starting slow and gradually speeding up gets it under your fingers faster than going straight in at the original tempo. Use a playback app or DAW that can lower the tempo while keeping the key, and step up in stages like these.

• Raising the speed 5–10% per stage lets you get used to it without strain
• With playback where the key changes (varispeed), 0.9× drops the pitch about 1.82 semitones, so a tuned guitar won’t match the recording. For practice, choose playback that keeps the key
• When practicing with a metronome, set it to the BPM multiplied by the ratio (0.8× of BPM 120 is 96)
• Before stepping up to 1× for the last time, playing it slightly fast at 1.05× makes the original tempo feel easy

FAQ

How much does the key go up if I take BPM 120 to 128?

With playback where pitch changes along with speed (varispeed), about 1.12 semitones. The playback speed is about 1.0667×, which is +6.67% on a DJ pitch fader. With key lock or time-stretching, the key doesn’t change.

What percentage of playback speed is one semitone?

About 5.95%. Raising the pitch one semitone multiplies the frequency by the 12th root of 2 (about 1.0595), so with playback where pitch follows speed, raising the speed about 5.95% raises it one semitone. Going down, about 5.61% slower (about 0.9439×) lowers it one semitone.

How many semitones lower is 0.75× playback?

With playback where the pitch changes too, about 4.98 semitones, almost exactly 5 (a perfect fourth) down. For instrument practice, choose time-stretch playback, which changes only the tempo and keeps the key.

How do I calculate the percentage for a DJ pitch fader?

It’s “(target BPM ÷ next track’s BPM − 1) × 100”. To match a BPM 124 track to 128: (128 ÷ 124 − 1) × 100 ≈ +3.23%.

What tempo raises the key by exactly one semitone?

Multiply the original BPM by about 1.0595. BPM 120 becomes about 127.14, and BPM 100 about 105.95. Two semitones is about 1.1225×, which takes BPM 120 to about 134.7.