1 Load your track
mp3 · aac · mp4 · wav · flac · ogg · m4a · avi and many more
2 Tempo & key
Adjust speed and pitch independently — slow down without changing the key
100% = original speed. 50% plays half as fast, 200% twice as fast. Values from 0.1% to 400% can be typed directly (decimals supported).
0 = original key. Negative values lower the key, positive values raise it; one step = one semitone, −12 = one octave lower. Decimals can be typed for fine adjustments (e.g. non-western tunings).
3 Output options
Format and processing algorithm
Depending on the input music one or the other algorithm produces better results. If the result sounds distorted, try the other one.
How to change the speed of a song
Changing the playback speed of a song without altering its pitch is called time-stretching. Select your file above, set the speed as a percentage of the original (50% = half speed, 200% = double speed), choose an output format, and click convert. The result keeps the original key, so chords and melodies stay recognizable even at slow practice tempos.
To change the key instead, adjust the pitch in semitones: −12 shifts the song a full octave down, +2 transposes it a whole step up. Decimal values allow fine adjustments, for example for recordings that are slightly off concert pitch or for non-western tunings. Speed and pitch are independent — you can combine both in a single conversion.
Who uses an audio speed changer?
Slow difficult solos to 50–75% to practice them note by note, then speed back up gradually.
Adjust the tempo of choreography music to match training pace.
Slow down dialogues and podcasts to catch every word, without the "chipmunk effect".
Transpose backing tracks into a comfortable key for your voice.
Match keys and tempos of tracks before mixing.
Slow recordings of interviews and lectures for accurate transcription.
Pitch vs. tempo — what's the difference?
On vinyl or tape, speed and pitch are coupled: play a record faster and it sounds higher. Digital signal processing decouples the two. A time-based algorithm cuts the audio into small overlapping segments and rearranges them, while a frequency-based algorithm transforms the signal into the spectral domain and scales it there.
Depending on the material — percussive vs. harmonic — one or the other gives cleaner results, which is why this converter offers both. If your result sounds distorted, simply convert again with the other algorithm. More background information can be found on the key & tempo info page.
Frequently asked questions
Is the converter really free?
Yes. The online converter is free and requires no account. It is financed by advertising. A paid offline desktop app with batch processing is also available.
Which input formats are supported?
mp3, aac, mp4, wav, flac, ogg, m4a, avi and many more.
What happens to my files?
Files are processed on the server and automatically deleted after conversion. Converted files are removed after one hour.
Can I change speed and pitch at the same time?
Yes — both parameters are independent and can be combined in a single conversion.
Why does my converted file sound distorted?
Try the other algorithm (time-based vs. frequency-based). Extreme settings far beyond ±12 semitones or below 50% speed naturally introduce artifacts.
Can I convert many files at once?
The online tool converts one file at a time. For batch conversion of complete music collections, use the offline desktop app (Windows and macOS).