Audio Time Stretching

Audio time stretching changes the speed and duration of a track without changing its pitch. Instead of playing the audio faster or slower like a tape or a record — which also raises or lowers the pitch — a time-stretching algorithm keeps every note in the same key while only the tempo moves. KeyPitch lets you stretch from ×0.5 (half speed, twice as long) up to ×2 (double speed, half as long).

Upload your MP3, WAV, M4A or MP4 file to KeyPitch and drag the Speed slider — anywhere from ×0.50 to ×2.00. The track instantly gets longer or shorter while the pitch stays exactly where it was. Preview the result, then click Download and your stretched file opens in the KeyPitch Audio Studio where you can fine-tune and export.

Time stretching changes the tempo and length of a track while keeping the pitch fixed. Pitch shifting does the opposite: it changes the pitch (key) while keeping the tempo and length fixed. They are two independent operations, and KeyPitch gives you both — the Speed slider for time stretching and the Pitch (Hz) slider for pitch shifting — so you can use one, the other, or both together.

Yes — that is exactly what audio time stretching is for. Move the Speed slider and the tempo changes while the pitch stays untouched: slow a song to half speed to learn a solo, or speed it up for an edit, and the key never moves. Old methods like vinyl or simple resampling tie the two together; KeyPitch keeps them separate.

Use the Speed slider. Setting it below ×1.00 stretches the track out so it runs longer; setting it above ×1.00 compresses it so it runs shorter. At ×0.50 the song lasts twice as long, at ×2.00 half as long — and because this is true time stretching, the pitch is identical at every setting. It is the easiest way to fit a track to a fixed video or scene length.

KeyPitch uses high-quality time-stretching (based on the SoundTouch engine) that processes time and pitch separately. It analyses the audio and rebuilds it at the new tempo while preserving the original frequencies, so the result stays clean and natural instead of sounding warped or robotic the way crude speed changes do.

Moderate stretching is virtually transparent. KeyPitch's high-quality algorithm keeps the audio clean across most of the range. Extreme settings — very slow speeds or large stretches combined with a pitch shift — can introduce subtle artifacts, which is normal for any time-stretching tool. Preview the result and start from a WAV or high-bitrate MP3 for the best quality.

KeyPitch covers ×0.5 to ×2, and most of that range sounds great. Gentle changes between about ×0.8 and ×1.3 are essentially flawless. As you push toward the extremes the audio holds up well but may pick up a slight smearing on busy material, so trust your ears: preview, and back off a little if you hear artifacts you do not like.

The chipmunk effect is the high, squeaky sound you get when audio is sped up the old way, with pitch and speed locked together. Time stretching avoids it completely by changing only the tempo and leaving the pitch alone — so a sped-up song still sounds like the original singer, just faster. If you ever do want that effect, raise the Pitch (Hz) slider on top of the speed.

Yes. The Speed slider is a tempo multiplier, so to reach a target BPM you divide the new tempo by the original. For example, to take a 120 BPM track to 100 BPM, set the speed to about ×0.83; to push it to 138 BPM, set roughly ×1.15. The pitch stays in the original key, which makes it ideal for mashups, DJ sets and lining two songs up to the same tempo.

Yes. The Speed slider and the Pitch (Hz) slider are independent, so you can stretch the time and shift the pitch in the same edit — for example slow a track down and retune it to 432 Hz at once. In the KeyPitch Audio Studio you also get a Semitones slider (±12) to transpose a full octave while the stretched tempo stays exactly as you set it.

Yes — install the KeyPitch Chrome Extension. It adds a speed and pitch panel directly on YouTube and YouTube Music, so you can slow a video down or speed it up live, with the pitch held in the original key, while it plays. Perfect for practising an instrument, transcribing a solo or singing along without any download.

Absolutely — this is one of the most popular uses of time stretching. Set the Speed slider to ×0.50–×0.75 and the song plays at half to three-quarter speed in the original key, so every note of a fast solo, riff or vocal run is easy to hear and copy. Speed it back up gradually as the part gets comfortable.

Yes. Upload an MP4 and the speed change is applied to its audio while the picture stays in sync, so a slowed or sped-up video keeps the same pitch on the soundtrack. In the Audio Studio you can export the result as MP4 if you uploaded a video, or as MP3 or WAV for audio only.

KeyPitch accepts MP3, WAV, M4A and MP4 files up to 50 MB and 10 minutes long. The time stretch is applied to the audio of any of them, and videos keep their picture in sync. In the Audio Studio you can export as MP3 or WAV — or as MP4 if you uploaded a video.

Yes. You can upload a song, stretch the time, shift the pitch and preview the result for free, with no signup. The full Audio Studio adds extra controls — semitone key shifting, reverb, bass boost, 8D audio and more — for the perfect export.