To move a song from its current BPM to a target BPM, divide the target by the source. For example, 120 to 90 BPM needs 0.75× speed. This guide covers the calculation, checking the BPM estimate, and exporting without changing the key.
If you know the source and target BPM, you can calculate the playback speed needed to match them. This is different from measuring what one “+1” step means on a karaoke machine: here, you choose the BPM you want the recording to reach.
Calculate the speed multiplier
Use target BPM ÷ source BPM = speed multiplier. A result below 1 slows the song down; a result above 1 speeds it up. Reversing the division moves the song away from your target.
| Source BPM | Target BPM | Calculation | Speed field |
|---|---|---|---|
| 120 | 90 | 90 ÷ 120 | 0.75× |
| 90 | 120 | 120 ÷ 90 | 1.33× |
| 128 | 110 | 110 ÷ 128 | 0.86× |
| 80 | 100 | 100 ÷ 80 | 1.25× |
Check the source BPM
- Open the audio in the key and BPM analyser and read its BPM estimate.
- If the analyser shows an alternative, listen to the beat and choose the value that matches how you count the song. A kick or snare pattern can be counted every other beat, producing a half-time or double-time reading.
- Use the source and target BPM in the formula. For example, 120 to 90 BPM is 90 ÷ 120 = 0.75.
Change the tempo while keeping the key
- Open the audio in Key & tempo change.
- Enter the calculated multiplier in the Speed control. Its current range is 0.50× to 2.00×. A target outside that range cannot be reached with this control.
- Leave Semitones and Cents at 0. After processing, check the estimated BPM shown by the tool and listen before exporting.
Keeping both pitch controls at 0 changes the tempo without shifting the key. A larger change can also alter how a recording sounds, so listen to the drum attacks and vocals instead of judging by the target number alone.
When the result misses the target
- The result is much too fast even with the calculated value. Check whether the source BPM was detected at half time; compare the alternative and listen to the beat.
- The displayed BPM is close but not exact. The source estimate can be off. Adjust the speed slightly and check that the beat still lands naturally.
- The multiplier is below 0.50 or above 2.00. That is outside this control’s range. Do not assume a large change will sound as accurate as a small adjustment.