Free Audio Speed Changer

Worked example

A 45-minute lecture at 1.5x with "Keep natural pitch" on becomes 30 minutes, and the voice keeps its normal pitch. Saved as MP3 at the default 192 kbps that is about 43 MB, and the size estimate under the output options shows the number before you press "Make it 1.5x". If the lecture must fit a 30-minute slot exactly, type 30:00 under "Target length" and the speed is set for you.

Which settings to use, and the limits

• Pick the pitch mode first. "Keep natural pitch" time-stretches the audio, so speech and music keep their pitch. Turn it off to change speed and pitch together, like a record played faster, as in nightcore or slowed edits.
• Use the one-tap vibes. "Nightcore" is 1.3x, "Sped up" is 1.25x, "Slowed + reverb" is 0.8x with medium reverb, and "Slowed, no reverb" is 0.85x. All use pitch-shift mode. You can change the speed afterwards.
• Know the speed range. Custom speed can be anything from 0.25x to 4x. For something more extreme, download the result, drop it in again and apply the speed a second time.
• Set speed by length, percent or BPM. Type a "Target length" such as 5:00, a "Tempo change (%)", or the song's current and target BPM, and the matching speed is filled in. If the result falls outside 0.25x to 4x, the tool says so.
• Trim first to save time. "Trim first" processes only the part between Start and End (use m:ss or seconds). Start must be before End and inside the file.
• Choose the output with care. WAV and FLAC stay lossless. MP3 and M4A offer 64 to 320 kbps and lose a little quality from a lossless source. "Mono" makes the file smaller. A video file gives back audio only. File limits depend on the device: about 2 GB on a computer and 400 MB on a phone.

Common problems and how to fix them

The speed I want is refused.

Speed is limited to 0.25x to 4x. A target length or BPM that needs more than that is flagged in red. Apply the change in two passes: process once, download, and drop the result in again.

The trim range is marked invalid.

Start must be before End and both must fall inside the file. Use m:ss, h:mm:ss or plain seconds. Leave End empty to go to the end.

Voices sound like chipmunks.

"Keep natural pitch" is off, or you picked a vibe preset, which turns pitch-shift on. Switch "Keep natural pitch" back on and listen in the player before encoding.

I pressed cancel and nothing was saved.

Cancelling discards the half-finished file. Press the button again to restart. Trimming to a shorter range makes a long file finish sooner.

How it compares

Time-stretching (Keep natural pitch) changes how long audio lasts without changing the pitch, which suits podcasts, lectures and audiobooks. Pitch-shifting changes speed and pitch together, which is the classic tape or record effect. Time-stretching at high speeds can sound slightly smeared on music with sharp beats, so for music edits pitch-shift mode is often the cleaner choice.