Drop
Choose one WAV. StemPrep fingerprints the source before it sends anything.
Source WAV
Open-source stem separation for macOS
Every stem.
Beside the source.
Drop a WAV, choose an MVSEP model, and collect every returned part in one tidy folder.
NativeBuilt with SwiftUI
UniversalIntel and Apple silicon
PrivateToken secured in Keychain
DirectYour Mac to MVSEP
A focused studio utility.
StemPrep keeps the source, model, progress and finished files visible without turning separation into a technical job.
From track to stems.
Three clear actions, with truthful remote progress and recovery built in for the parts that take time.
Choose
Pick from the live MVSEP model catalogue and select WAV, FLAC or MP3 delivery.
Exact model settingsCollect
Every returned stem lands beside the source with a manifest and an original copy.
One sibling folderBuilt for real separation jobs.
Long uploads, remote queues and interrupted sessions are treated as normal, recoverable states.
Resume without uploading twice
Accepted MVSEP jobs remain recoverable after the app closes or the network drops.
Handle large WAVs safely
A temporary file-backed upload avoids holding the full WAV in memory and is removed after submission.
See the remote job clearly
Queue position and real large-file chunk progress appear directly across the source waveform.
Native from the Dock
Universal SwiftUI app for Intel and Apple silicon Macs.
Recover and re-download
Browse available MVSEP history, restore finished jobs and cancel eligible queued work from the app.
Your token stays on your Mac.
StemPrep has no analytics, ads or developer-operated server. Your API token is stored in macOS Keychain.
When you start a job, the WAV and selected settings go directly to MVSEP. Their privacy policy governs that processing.
Read the privacy detailsFirst run makes the connection clear.
StemPrep points to MVSEP's Full API page, explains where to find the token, then saves it securely.
Open MVSEP API setup
Before you download.
The practical details for the current release.
Does StemPrep separate audio locally?
No. The macOS app sends the chosen WAV directly to MVSEP and downloads the returned stems.
Do I need a paid MVSEP account?
You need an MVSEP account and API token. Queue priority, limits and available exports depend on your MVSEP plan.
Where are finished files saved?
In a new folder beside the source WAV, named after the track with “Stems” appended.
Is the app signed and notarized?
Version 1.1 is ad-hoc signed but not notarized with an Apple Developer ID. Right-click the app and choose Open if macOS asks for confirmation.
Can I inspect or build it myself?
Yes. The complete Swift source, tests and build scripts are available under the MIT license.
Ready for the next split.
Open source, universal and designed for macOS 14 or newer.