Change Audio Speed
Processing entirely on your device — large files may take a moment.
The atempo filter resamples playback time: 0.5× doubles the duration, 2× halves it. The pitch follows the speed (like vinyl at the wrong RPM), which is exactly the effect DJs and sound designers reach for — and it keeps speech surprisingly usable down to about 0.75×.
The 0.5×-2× range is what the audio filter handles in one pass; chain the tool twice for 4× (2× then 2× again).
How to change audio speed
- 1
Select your files
Drag & drop your MP3 files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to MP3". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted MP3 file individually, or grab everything at once as a ZIP archive.
About the MP3 format
MP3 (MPEG-1 Audio Layer III) defined digital music: standardized in 1993, popularized by Napster and the first portable players, and freed of all patents in 2017. It is lossy psychoacoustic compression — it discards frequencies the ear supposedly won't miss — at bitrates from 128 to 320 kbps, with ID3 tags carrying title, artist and cover art.
Twenty years of competitors have failed to displace it, because playback support is absolute: every device that has ever played music plays MP3. At 320 kbps even critical listeners struggle to identify it in blind tests, though modern codecs reach the same quality at noticeably lower bitrates.
+Strengths
- ✓Plays on absolutely everything
- ✓Rich tag ecosystem (ID3, cover art)
- ✓320 kbps is transparent for most listeners
!Limitations
- −Lossy ceiling — never a mastering format
- −Less efficient than AAC/Opus at equal quality
- −Low-bitrate artifacts are audible and permanent
Frequently asked questions
Does the pitch change?
Yes — that is inherent to resampling. Pitch-preserving speed change needs a phase vocoder; if you want slower-but-same-pitch, that is a different (heavier) effect.
Can I make a slowed+reverb style track?
The slowed half, yes — 0.85×-0.9× is the classic rate. Reverb needs an extra effect pass this tool does not include.
Why not 3× speed?
atempo is hard-limited to 0.5-2.0 per pass. Chain the tool twice for 4×.