Set an MP4 to 66% speed

Add or drop a file here

Add file

66% speed

0.66x 34% slower

Need to change BPM while the track is already playing?

Use the BPM Changer extension when you want to slow down or speed up streaming audio in real time and keep rehearsal moving.

Install the extension

Common questions

How do I change the speed of a song or audio file?

Add a local file, choose a preset or move the slider, and let the tool prepare the new version. Lower percentages slow the file down, and higher percentages make it play faster.

Will changing the speed also change the pitch?

No. This tool keeps the pitch steady while changing playback speed, so you can compare the pacing without the file drifting to a different key.

What speed should I try first?

If you are unsure, start with 90% for a light slowdown, 75% for a more obvious rehearsal pace, and 125% if you want to check whether the material still feels comfortable slightly faster.

Does my file stay on this device?

Yes. This tool handles the file locally on your device, so it never needs to be uploaded to a server.

What does the download button export?

The download button exports a WAV result generated locally after the selected change is processed.

What this preset does

It opens with the slider already set to 66% speed, so you can hear the pacing change right away.

When to try it

Use it when you want an MP4 at 66% speed and need a clear starting point before nudging the slider manually.

What to compare next

If this setting feels close but not final, compare it with 76% speed or head back to the broader MP4 Speed Changer guide for manual fine-tuning.

Why this preset helps

It gives you a focused starting point inside MP4 Speed Changer instead of making you dial in the same speed from scratch every time.

Speed-change basics worth keeping nearby

Keep this quick reference nearby when you are comparing slower and faster versions. It covers what changes when speed moves, how duration reacts, and which practical playback settings musicians reach for most often.

What speed change does

Speed change moves playback earlier or later in time. Lower percentages slow the file down, higher percentages move it faster, and the pitch-preserving process keeps the musical key from drifting with the speed.

Why duration changes matter

Slower playback gives you more time to hear detail, while faster playback shortens the file and helps you test fluency or pacing. Duration is part of the musical feel, not just a side effect.

What to listen for

Compare clarity, articulation, breath points, groove, and whether the phrase still feels natural at the new pace. Small changes are often enough for rehearsal work.

Common applications

Slowing down tricky passages for practice without changing the key center
Checking whether a vocal or instrumental phrase still feels natural at a brisker pace
Preparing slower rehearsal versions before stepping back toward performance speed
Comparing groove and articulation without opening a larger editor
Making quick practice references that stay in the original key

Practical speed anchors

These are the settings musicians reach for most often when they want a quick slower-or-faster comparison without guessing from scratch.

Setting	Multiplier	Duration	Typical use
50% speed	0.5x	2x duration	Extreme slow practice when you need every entrance and subdivision to feel exposed.
75% speed	0.75x	1.33x duration	A common rehearsal slowdown when the passage is close but still moving too quickly.
90% speed	0.9x	1.11x duration	A small slowdown that keeps the phrase feeling musical while adding breathing room.
100% speed	1x	Same duration	Original pace for checking how the phrase really sits before or after comparisons.
110% speed	1.1x	1.1x shorter	A gentle push when you want to test whether the material stays comfortable slightly faster.
125% speed	1.25x	1.25x shorter	A stronger tempo lift for articulation and fluency checks once the notes already feel settled.
150% speed	1.5x	1.5x shorter	Fast review mode when you want to pressure-test clarity and pacing.
200% speed	2x	2x shorter	A dramatic speed jump for quick navigation or extreme fluency checks.

Nearby presets

MP4 Speed Changer 60% speed

Preset for setting an MP4 to 60% speed.

60%

MP4 Speed Changer 70% speed

Preset for setting an MP4 to 70% speed.

70%