MyMP3 Converter How to slow down or speed up an audio file on iPhone
Open the file on the Audio tab, tap Speed, move the Speed slider between 0.5x and 2.0x, tap Apply & Save. You get a new copy at the new speed, same pitch, and the original is left exactly as it was.
★ 4.6 (29) Why change the speed of a recording
Slowing audio down helps with learning a solo note by note, and it works just as well for catching every word of a fast speaker or transcribing an interview. Speeding up gets you through a long lecture or meeting in less time. Pitch stays put either way, so nobody ends up sounding like a chipmunk or a monster.
How to slow down audio on iPhone, step by step
- Get the recording into the app: convert a video, or tap + on the Videos tab to import an audio file (a voice memo saved to Files, an MP3) and convert it.
- Go to the Audio tab and tap the file.
- Tap Speed to open the Speed & Pitch panel.
- Move the Speed slider; it runs 0.5x to 2.0x in steps of 0.25.
- Tap Apply & Save. A new file with _fx in the name shows up on the Audio tab.
- Open it to check, then share or export like any other file.
How long will the new file be?
New length is just the original divided by the speed. For a 3-minute recording:
| Speed | New length |
|---|---|
| 0.5x | 06:00 |
| 0.75x | 04:00 |
| 1.25x | 02:24 |
| 1.5x | 02:00 |
| 1.75x | 01:42 |
| 2.0x | 01:30 |
A 50-minute lecture at 1.5x drops to 33:20; at 2.0x, 25:00.
How to change the pitch of audio on iPhone (Pro)
With Pro, the Pitch slider in that same panel shifts the sound up or down by up to 12 semitones, one semitone (100 cents) at a time. Use it alone or stack it with a speed change.
| Slider | Semitones | Frequency ratio |
|---|---|---|
| -1200¢ | -12 (one octave down) | 0.5 |
| -300¢ | -3 | 0.8409 |
| +100¢ | +1 | 1.0595 |
| +300¢ | +3 | 1.1892 |
| +500¢ | +5 | 1.3348 |
| +1200¢ | +12 (one octave up) | 2.0 |
Musicians reach for this to move a backing track into a key that fits their voice or instrument — +300¢, say, raises a song by 3 semitones.
Tips and common mistakes
- Extreme settings, 0.5x or 2.0x, add a slightly watery sound. For practice, 0.75x is usually the sweet spot.
- The new file saves as M4A no matter the original format. Convert again if you need MP3 out of it.
- Speed is free; the Pitch slider stays locked on the free tier.
- This only works on files. It won’t speed up audio while another app is playing it live.
Speed and pitch together
Both sliders live in the same Speed & Pitch panel and apply together on Apply & Save: a slower 0.75x with a +300¢ (3-semitone) pitch shift, say, gets you a different key at a different length in one pass, so there’s no second file to juggle.
Questions and answers
Can you slow down audio on iPhone without changing the pitch?
Can I speed up voice memos?
Is changing the speed free?
Does it overwrite my original file?
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