What does the tempo changer do?

The tempo changer adjusts the playback speed of an audio file. At 2× speed, the audio plays twice as fast and lasts half as long. At 0.5×, it plays half as fast and lasts twice as long. This tool uses browser playbackRate processing, which also shifts pitch proportionally.

Does changing tempo also change the pitch?

Yes, with this tool. Speeding up also raises the pitch; slowing down lowers it. This is the standard rate-change approach available in the browser's Web Audio API. True time-stretching (speed change without pitch change) requires a more complex phase-vocoder algorithm not yet included here.

What speed range is supported?

Speed from 0.25× (one quarter speed) to 4× (four times speed). At 0.25× a 1-minute clip becomes 4 minutes; at 4× it becomes 15 seconds.

What formats can I speed up?

Any format your browser decodes: MP3, WAV, OGG, FLAC, AAC/M4A, and WebM. Output is WAV (16-bit PCM).

Is the audio uploaded to a server?

No. Speed changing uses the Web Audio API OfflineAudioContext with a playbackRate-adjusted source node. Everything runs locally.

Can I use this to listen to a lecture or podcast faster?

Yes. Set speed to 1.5× or 2× to save time on spoken content. Bear in mind that pitch will rise accordingly — voices will sound higher. For pitch-preserved speed changes, a desktop app such as Audacity or VLC is recommended.

What happens to the output duration?

Output duration = original duration ÷ speed factor. A 3-minute file at 1.5× becomes 2 minutes. The tool shows the expected output duration before you process.

Can I preview the result before downloading?

Yes. After processing, an audio player appears with the speed-changed result. Adjust and re-process if needed.

Tempo Changer

Speed up or slow down audio from 0.25× to 4×. Supports MP3, WAV, OGG, FLAC, and M4A — all in your browser, no upload.

100% in your browser. Your file never leaves your device.

Audio file

Speed: 1.00×

0.25× (slow) 1× (original) 4× (fast)

Load an audio file to begin.

How to change audio tempo

Choose your audio file. The original duration is shown after loading.
Drag the speed slider or click a preset button (0.5×, 1.5×, 2×, etc.).
The expected output duration updates as you adjust the speed.
Click Apply Speed Change and wait for processing.
Preview the result and download the WAV file.

Common use cases

Study faster: Speed up lectures or audiobooks to 1.5× or 2× to save time.
Slow-motion audio: Slow down a complex musical passage to analyse it.
Shortening a clip: Speed up background music to fit a video of a fixed length.
Practice tool: Slow down a fast musical piece to practice along at reduced speed.
Creative effects: Apply extreme speeds for chipmunk or deep-voice effects.

Related tools: Pitch Shifter · Audio Trimmer · Audio Fade · Volume Normalizer

常見問題

What does the tempo changer do?: The tempo changer adjusts the playback speed of an audio file. At 2× speed, the audio plays twice as fast and lasts half as long. At 0.5×, it plays half as fast and lasts twice as long. This tool uses browser playbackRate processing, which also shifts pitch proportionally.
Does changing tempo also change the pitch?: Yes, with this tool. Speeding up also raises the pitch; slowing down lowers it. This is the standard rate-change approach available in the browser's Web Audio API. True time-stretching (speed change without pitch change) requires a more complex phase-vocoder algorithm not yet included here.
What speed range is supported?: Speed from 0.25× (one quarter speed) to 4× (four times speed). At 0.25× a 1-minute clip becomes 4 minutes; at 4× it becomes 15 seconds.
What formats can I speed up?: Any format your browser decodes: MP3, WAV, OGG, FLAC, AAC/M4A, and WebM. Output is WAV (16-bit PCM).
Is the audio uploaded to a server?: No. Speed changing uses the Web Audio API OfflineAudioContext with a playbackRate-adjusted source node. Everything runs locally.
Can I use this to listen to a lecture or podcast faster?: Yes. Set speed to 1.5× or 2× to save time on spoken content. Bear in mind that pitch will rise accordingly — voices will sound higher. For pitch-preserved speed changes, a desktop app such as Audacity or VLC is recommended.
What happens to the output duration?: Output duration = original duration ÷ speed factor. A 3-minute file at 1.5× becomes 2 minutes. The tool shows the expected output duration before you process.
Can I preview the result before downloading?: Yes. After processing, an audio player appears with the speed-changed result. Adjust and re-process if needed.

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