If slowing a track down also makes it sound flat, the player is changing the sample rate instead of time-stretching. You need a tool that separates speed from pitch. On a Mac, JamCrate slows audio from 1.0× down to 0.5× with the pitch preserved, and keeps your markers and tab on screen while it does — but it deliberately does not go above the original speed.
Why slowing down normally goes flat
Digital audio is a stream of samples at a fixed rate — 44100 or 48000 per second. The cheap way to play it slower is to push those samples out at a lower rate: 22050 instead of 44100. Everything stretches, including the frequencies, so the whole track lands an octave lower. That is exactly what a turntable does when you drop the speed, and it is why the old trick of learning a solo at half speed meant learning it in the wrong key.
What time-stretching does instead
Time-stretching analyses the audio in short overlapping windows, works out where the pitched content is, and rebuilds it over a longer duration while leaving the frequencies alone. The result is a track at 70% speed that is still in E. It is not free: the more you stretch, the more the algorithm has to invent, and dense distorted mixes start to sound smeared. Practically, 0.5× is usable, 0.3× is mush, and acoustic material survives better than a wall of guitars.
How to actually use it
- Find your clean tempo. Start slower than you think you need. If you make a mistake, you are still too fast.
- Loop the hard bars, not the whole solo. Four bars on repeat for five minutes beats the whole solo once. See looping a solo.
- Climb in small steps. When it is clean three times in a row, go up about ten percent. Going from 60% straight to 100% teaches you nothing except where you fail.
- Finish at full speed. The point of slowing down is to be able to leave it. End every session with a couple of passes at 1.0×.
The options on a Mac
| Tool | Slows down | Keeps pitch | Notes |
|---|---|---|---|
| JamCrate | 0.5×–1.0× | yes | markers, loops and tab stay on screen; no speed-up above 1.0× |
| QuickTime | yes | — | no markers and no A/B loop; fine for a listen, not for drilling |
| Audacity | yes | yes, with Change Tempo | Change Tempo preserves pitch, Change Speed does not — easy to pick the wrong one |
| A DAW | yes | yes | best quality and most control; also the slowest thing to open |
| Anytune / Moises | yes | yes | mature practice features on a subscription, per file rather than per library |
While you are at it: why some tracks are louder than others
The other half of practising with a folder of tracks is volume. A mastered commercial backing track and a home-made jam track can sit twelve decibels apart, so every song change is a reach for the volume knob. JamCrate measures each file once when it is imported and stores a gain correction, so tracks arrive at roughly the same perceived level. The correction is limited to about ±12 dB, which means a badly recorded file will not be blasted into distortion just to hit a target.
Try it on a track you already own
JamCrate is a free beta for macOS 14+. Import a folder, mark the hard bars, take the tempo down to 0.5× and keep the key.
Download for Mac Try the player in your browser
About 6 MB · Universal build · signed and notarized by Apple · no account, nothing leaves your Mac.
Prefer Homebrew? brew install --cask vitas/jamcrate/jamcrate
Questions
Does slowing down damage my audio file?
No. Time-stretching happens during playback; the file on disk is never rewritten. Set the tempo back to 1.0× and the track is untouched.
Can I practise with a slowed track on my phone?
Yes — the set can open on a phone in the same Wi-Fi and the audio streams from the Mac, with the transport and the solo loops on the phone screen.
Why only down to 0.5×?
Below half speed the artefacts get loud enough that you start learning the smearing instead of the notes. If you genuinely need 0.3×, a DAW will do it better.