Change the tempo of a song
Choose a song and StemVocal reads its tempo, so you can type the BPM you want instead of guessing a percentage. The speed slider covers everything from half speed to double speed. Press Change tempo and the whole song is made again at the new speed, with its key unchanged. Play it back, then download the WAV, or make a 320 kbps MP3 copy.
Your settings stay in place, so you can try another tempo and compare.
Keep the key while the speed changes
Speeding up a record on a turntable raises its pitch along with the tempo. This tool changes them independently: it lengthens or shortens the sound without moving its notes, so a song slowed from 120 to 100 BPM stays in its original key. To move the key as well, choose a number of semitones under Key before you press Change tempo; the key changer explains how semitones map to keys.
Common reasons to change a tempo
- Practice. Slow a solo or a fast passage to 75% until you can play it cleanly, then step back up.
- DJ sets. Bring a song to the tempo of the one before it, for example from 124 to 128 BPM, so the beats line up.
- Workouts and dance classes. Match a routine that is counted at a fixed tempo.
- Content. Fit a song to the length of a video by nudging its speed a few percent.
Getting a natural sound
Time-stretching works best in small steps: the smaller the change, the less you hear it. Large changes can soften drum hits and give long notes a slight phasing. For practice at very slow speeds, the acapella extractor's practice player can also slow down and loop just the part you are learning, before you download anything.
Finding the original tempo
The tempo shown for your song comes from the same analysis as the BPM finder. If it reads half or double the tempo you hear, use the BPM finder's Half and Double buttons to check, then type the target tempo here. The speed percentage is what actually changes, so the result is right even when the reading is off by an octave.