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Change Audio Speed Without Changing the Pitch

Slide the speed anywhere from 0.25x to 4x, keep the original pitch or let it drop and rise like a tape, then save the result as MP3, WAV or M4A. It all happens in this browser tab, right where your file already sits.

Processed on your device with ffmpeg.wasm. Your file is never uploaded anywhere.

音声ファイルをここにドロップ

またはクリックして端末から曲を選ぶ

MP3・WAV・M4A・AAC・OGG・FLAC · 200 MB まで

無料オーディオツール

音声形式変換

MP3・WAV・OGG・AAC・FLAC・M4Aを相互に変換

音声カット

MP3・WAV・M4A をカットして着信音も作れます

着信音メーカー

好きな曲を iPhone の .m4r や Android の MP3 着信音に

MP3タグエディター

再エンコードせずに ID3 タグとジャケット画像を編集

BPM 判定

曲のテンポを小数第1位まで、タップ不要で測定

タップBPM

曲に合わせてタップするだけでテンポがわかる

WAV to MP3

MP3・WAV・OGG・AAC・FLAC・M4Aを相互に変換

M4A to MP3

MP3・WAV・OGG・AAC・FLAC・M4Aを相互に変換

オンラインメトロノーム

無料のメトロノームで完璧なタイミングを。

オンラインチューナー

楽器を正確にチューニング。

エフェクト付きボイスレコーダー

プロのオーディオエフェクトで声を録音・変換。

ミュージックビジュアライザー

音楽に合わせて踊る素晴らしいビジュアルを観賞。

オンライン MIDI エディター

ブラウザで音符ごとに作曲。

五度圏

インタラクティブな五度圏で音楽理論をマスター。

音符周波数計算器

任意の音符の正確な周波数を計算。

リズムゲーム

あなたの音楽でリズムゲームをプレイ。

無料オンラインMusicXMLプレーヤー

MusicXML楽譜を読み込み、リアルなSalamanderグランドピアノのサンプルで再生

How the speed change works

With Keep the Pitch on, the tool runs FFmpeg's atempo filter. Atempo slices the audio into small overlapping windows, then stretches or compresses the gaps between them so the track plays back slower or faster while every note stays in its original key. It is the same idea a podcast app uses for 1.5x playback, just running locally instead of on a phone chip.

With Keep the Pitch off, the tool switches to asetrate instead. Asetrate relabels the sample rate the audio is read at without touching the samples themselves, so a slower rate stretches every waveform out, dropping the pitch, and a faster rate compresses it, raising the pitch, exactly the way a cassette or vinyl record sounds when you change its motor speed.

Picking a speed for the job

For practice and transcription, slow to 0.5x to 0.8x with the pitch kept on, so a fast run or a mumbled lyric becomes easy to follow without the melody dropping into a different, confusing key. For lectures and podcasts, most people land between 1.25x and 1.75x with the pitch kept; anything faster starts to sound clipped and hard to parse even though the words are technically all there.

For matching a video edit, nudge the speed by a small amount, often under 10 percent, either way; the pitch shift at that range is barely noticeable, so leaving Keep the Pitch off is usually fine and gives a slightly warmer, more analog result. For a deliberate creative effect, like a big pitch drop or a chipmunk-style speed up, turn the pitch keeping off and push the slider further.

Quality limits and practical notes

Time-stretching has a comfortable range. Between 0.5x and 2x with the pitch kept, the result is close to transparent on most music; go further in either direction and you will start to hear a metallic flutter on sustained notes and vocals, because the algorithm is repeating or dropping more of the small windows it works with. The tape-style mode does not have that ceiling, but very slow settings can make bass turn muddy and very fast settings can make a voice sound thin and small.

Export as WAV if you are going to process the file again, since it carries no extra compression loss; MP3 or M4A are fine for listening back or sharing. Processing happens at your device's own speed, so a ten-minute file on a modern laptop finishes in a few seconds, while an older phone will take noticeably longer, especially at the more extreme ratios.

Speed change blueprint

The range behind the slider, and what each mode is actually doing to the sound.

Range0.25x to 4x playback speed
Default1x, unchanged speed, so you always start from the original
Best forPractice and transcription (slow), lectures and podcasts (fast), video sync (either)
Pitch behaviourKeep the Pitch on: pitch stays fixed. Off: pitch rises with speed, drops when slowed
Quality noteCleanest between 0.5x and 2x with pitch kept; tape mode has no such ceiling
OutputMP3, WAV or M4A
LimitsUp to 200 MB per file, processed entirely in this browser tab

How to Change Audio Speed Online

Three steps, all inside your browser

1

Add your audio

Drop in an MP3, WAV, M4A, AAC, OGG or FLAC up to 200 MB. The file loads straight from your disk and stays there.

Tips: A longer file just means a longer render, not a quality penalty.

2

Set the speed

Drag the slider anywhere between 0.25x and 4x, then turn Keep the Pitch on to hold the original key or off for a tape-style pitch shift.

Tips: 0.75x with the pitch kept is the usual setting for slow, accurate practice.

3

Preview and download

Play the new speed back right in the tool, then save it as MP3, WAV or M4A.

Tips: Choose WAV if you plan to edit the result again in another program.

Frequently Asked Questions

Everything about changing audio speed in the browser

No. The file is decoded and processed by ffmpeg.wasm, a WebAssembly build of FFmpeg running inside the browser tab. Nothing is sent to a server, so the whole speed change happens on your own device.
You can load MP3, WAV, M4A, AAC, OGG or FLAC up to 200 MB. Once the speed is changed, you save the result as MP3, WAV or M4A, whichever fits where you are taking it next.
With Keep the Pitch on, the time-stretch algorithm can add a faint warble or graininess if you push past roughly 2x or below 0.5x, since it is stitching small windows of audio together. With it off, the tape-style mode just resamples the file, so it stays clean at any ratio but the pitch moves with it.
On, the tool time-stretches the audio so the key stays exactly where it was, only the duration changes. Off, it behaves like a tape or turntable running faster or slower, so the pitch rises with speed increases and drops when you slow down.
Musicians slow a solo down to 0.75x to learn the notes, transcribers do the same for a fast vocal line, students and podcast listeners speed lectures up to save time, and video editors nudge a track to match a cut.
Not quite. This page changes duration first and pitch second. If you want the notes to move up or down while the length stays the same, use the Pitch Shifter instead.

Other one-click audio effects

Same ffmpeg engine running in your browser, each page doing one job.

Need a brand-new track instead of an edit to an existing one? AI 音楽生成

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スターター

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AIボーカル除去
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AIマスタリング
音楽アナライザー
AIカバージェネレーター
無制限(音楽ダウンロード)
商用ライセンス
リミックス＆編集
AI歌声モデルトレーニング
メールサポート