Audio speed changer
Choose an audio file, set a speed between 0.25× and 4×, and render a new WAV. The length changes by the inverse of the speed, and the pitch changes with it, like a tape or record played at a different speed.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose an audio file.
- Set the Speed with the slider or the number box, or tap a preset.
- Check the new length and the pitch change shown below.
- Press Change speed, listen to the preview and download the WAV.
How it works
The decoded samples are played into an offline audio context through a buffer source whose playbackRate is the chosen speed, and the rendered result is written as a 16-bit WAV. This changes duration and pitch together. Speeds are limited to 0.25x to 4x, and the result to 10 minutes.
Worked example
A 3-minute song at 1.25x lasts 144 s (2:24) and sounds 12 × log2(1.25), about 3.9 semitones, higher.
Tips
- Small changes (0.9x to 1.1x) are enough to practise along with a recording without it sounding odd.
- If you need the original pitch at a different tempo, use an editor with time-stretching; this tool does not do that.
Frequently asked questions
Does the pitch stay the same?
No. The audio is played through a resampler at the chosen rate, so pitch changes together with speed: 2x is one octave higher, 0.5x one octave lower. There is no time-stretching, so the pitch cannot be kept constant here.
How is the new length calculated?
The original length divided by the speed. A 60 s file at 1.5x becomes 40 s; at 0.5x it becomes 120 s.
What does the semitone figure mean?
It is the pitch shift caused by the speed change: 12 times the base-2 logarithm of the speed. 2x gives +12 semitones, 0.5x gives -12, 1.5x gives about +7.0.
Which formats can I use?
Any audio your browser can decode, such as MP3, WAV, M4A or OGG. The result is always a 16-bit WAV file.