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Pymss

pymss.net

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Spec score 8.7 #5 of 26 in AI stem splitters

What it is

Pymss is an open-source music source-separation toolchain that runs on the user's own machine and separates audio into vocals, drums, bass, and other stems. Its Studio desktop workspace handles model management, batch jobs, and stem editing. Users can import files or folders, choose a downloaded model, configure inference, and queue work. Studio can browse, download, resume, and delete model files, with storage cleanup controls. Waveform previews, mix controls, saved projects, and stem export support work on the results. Pymss can chain models so each workflow step uses the preceding step's output. The inference package lists WAV, FLAC, MP3, M4A, AAC, Opus, Vorbis, and Ogg output. Other components include ComfyUI custom nodes, a VST3 ARA plugin for compatible DAWs, and a browser interface bundled with the server. The ARA plugin provides per-stem mute and solo controls; its README gives Reaper and Studio One as host examples. The repositories have separate licenses: Studio is listed under AGPL-3.0 and the inference package under MIT. Studio remains at an early development stage, and changes between versions may break things.

Spec sheet

What it does
PyMSS is an open-source music source-separation toolchain for isolating vocals, instruments and other stems.Read 14 Oct 2026 · pymss.net
Purpose
Pymss is an open source music source separation toolchain that separates vocals, drums, bass, and other stems on the user's machine.Read 30 Sep 2026 · pymss.net
Platforms
The official site lists Windows, macOS, and Linux for Studio and CLI, iOS and Android for the mobile runtime, and Windows for the ARA plugin.Read 30 Sep 2026 · pymss.net
Integrations
The project provides ComfyUI custom nodes and a VST3 ARA plugin for use in DAWs.Read 30 Sep 2026 · pymss.net
Support
The project points users to GitHub documentation and an issue tracker, and its Studio README lists a QQ group for Chinese beta testing, bug reports, and community discussion.Read 30 Sep 2026 · pymss.net
ARA integration
The ARA VST3 plugin separates DAW tracks into stems in a background worker and supports per-stem mute and solo monitoring.Read 14 Oct 2026 · github.com
ARA plugin
The ARA plugin separates tracks inside an ARA-capable DAW and provides per-stem mute and solo controls; its README names Reaper and Studio One as example hosts.Read 30 Sep 2026 · github.com
Audio utilities
Included tools cover conversion, inspection, SDR and SI-SDR evaluation, speech recognition, vocal-to-MIDI, silence slicing and audio merging.Read 14 Oct 2026 · github.com
Browser interface
The WebUI is described as a browser interface bundled with the server and shipped with the pip package.Read 30 Sep 2026 · pymss.net
CLI
The command line supports inference, workflows, ComfyUI JSON execution, ensembles, model registration and server startup.Read 14 Oct 2026 · github.com
ComfyUI integration
Comfy-MSS provides nodes for catalog, custom-model and VR/UVR separation inside ComfyUI.Read 14 Oct 2026 · github.com
Custom models
Users can import weights and configurations for supported model architectures.Read 14 Oct 2026 · github.com
Development status
The Studio README says the app is at an early stage of feature development and breaking changes may occur between versions.Read 30 Sep 2026 · github.com
Editing and export
Studio provides waveform preview, mix controls, project persistence, and stem export.Read 30 Sep 2026 · github.com
External usage
The RVC project describes its PyMSS integration as providing model cataloging, downloading, audio I/O and ensemble utilities.Read 14 Oct 2026 · codeassuranceindex.info
Formats
The inference package lists WAV, FLAC, MP3, M4A, AAC, Opus, Vorbis, and Ogg as supported output formats.Read 30 Sep 2026 · github.com
HTTP API
The optional server extra provides a self-hostable HTTP service with dynamic model loading, catalog browsing, downloads and an optional WebUI.Read 14 Oct 2026 · github.com
Import and batch
Studio can import audio files or folders, select a downloaded model, configure inference, and queue jobs.Read 30 Sep 2026 · github.com
Licensing
The main Python package is MIT licensed according to PyPI.Read 14 Oct 2026 · pypi.org
Limit: Intel Mac
There is no dedicated Intel Mac package; source builds require checking inference dependency compatibility.Read 14 Oct 2026 · github.com
Limit: Linux packaging
The current release workflow does not provide Linux installers.Read 14 Oct 2026 · github.com
Limit: mobile
iOS and Android GPU or NPU support is described as future research, with no mobile application release currently provided.Read 14 Oct 2026 · github.com
Limit: model terms
The project warns that repositories and model weights can have separate licences and usage terms.Read 14 Oct 2026 · pymss.net
Limit: online preview
The online workspace uses included audio and preset stems, so processing personal audio requires downloading Studio or deploying PyMSS with WebUI.Read 14 Oct 2026 · pymss.net
Limit: prerelease
The Studio README warns that releases include prereleases and may contain breaking changes.Read 14 Oct 2026 · github.com
Local processing
Studio and local PyMSS installations process audio on the user’s device; runtime and model downloads need internet access.Read 14 Oct 2026 · pymss.net
Maintainers
PyPI lists two maintainers, baicai1145 and KitsuneX07.Read 14 Oct 2026 · pypi.org
Maturity
PyPI classifies PyMSS as Alpha software.Read 14 Oct 2026 · pypi.org
MNN runtime
PyMSS MNN supplies a C++ MNN inference runtime and conversion tools; Torch is used only for offline conversion.Read 14 Oct 2026 · github.com
Model ensembles
Studio can combine multiple models and stems with selectable ensemble algorithms and weights.Read 14 Oct 2026 · github.com
Model library
The model library supports search, favorites, notes, resumable downloads, storage controls and default inference parameters.Read 14 Oct 2026 · github.com
News: release 2.1.8
PyMSS 2.1.8 was released on October 8, 2026 with MLX warmup, bounded model caching and corrected batch progress.Read 14 Oct 2026 · github.com
Official plugins
The plugin registry lists loudness normalization, timing, dynamics, spectral processing, audio analysis and vocal-to-MIDI plugins.Read 14 Oct 2026 · github.com
Organisation
Hugging Face identifies pymss-project as a non-profit organisation with three team members.Read 14 Oct 2026 · huggingface.co
Platform support
Studio releases target Windows x64 and macOS 14 or later on Apple Silicon; Linux currently requires building from source.Read 14 Oct 2026 · github.com
Plugin extensibility
Plugins can register capabilities, workflow nodes and CLI commands through standard Python packages.Read 14 Oct 2026 · github.com
Python API
The Python package exposes MSSeparator, model registration and processing methods for catalog or custom models.Read 14 Oct 2026 · github.com
Python compatibility
PyPI declares Python 3.10 or newer and classifies the package as operating-system independent.Read 14 Oct 2026 · pypi.org
Source separation
Studio accepts audio, video or folders and supports batch processing with configurable models, devices, formats, folders and naming rules.Read 14 Oct 2026 · github.com
Stem editor
The editor includes multitrack waveforms, clip editing, transport, volume and pan, mute and solo, fades, effects, recording, project persistence and mix export.Read 14 Oct 2026 · github.com
Studio
Pymss Studio is a desktop workspace for model management, batch jobs, and stem editing.Read 30 Sep 2026 · github.com
Studio licence
Pymss Studio is licensed under GNU AGPL version 3.0.Read 14 Oct 2026 · github.com
Studio workspace
PyMSS Studio combines model management, separation jobs, batch processing, stem editing and mix export in a desktop application.Read 14 Oct 2026 · github.com
System requirements
Development requires Node.js 22, pnpm 10.33.2, Rust and Cargo, Python 3.12, and platform WebView or WebKitGTK dependencies.Read 14 Oct 2026 · github.com
WebUI
The separate WebUI is a Svelte and Vite browser interface that proxies health and /v1 requests to a local PyMSS server.Read 14 Oct 2026 · github.com
Workflow editor
Studio provides simple and advanced node-based workflow editors with import and export.Read 14 Oct 2026 · github.com
Workflows
Pymss can chain models into processing workflows, with each step using the previous step's output.Read 30 Sep 2026 · pymss.net

Plans and prices

Pymss Free Free · open source · runs locally Read 30 Sep 2026 · pymss.net

Every Pymss plan and price →

Strong points and limits

Strong points

  • Runs separation on the user's own machine
  • Studio supports batch jobs and stem editing
  • Can chain models into workflows
  • Lists eight output formats
  • Includes ComfyUI nodes and a VST3 ARA plugin

Limits

  • Studio is at an early development stage
  • Breaking changes may occur between versions
  • Repositories use separate licenses

Who it suits

Pymss suits people who want to separate music stems locally and manage batch processing or edits in a desktop workspace. It also offers components for ComfyUI users, compatible DAWs, and browser-based workflows.

Verdict

Pymss combines local stem separation with desktop batch and editing tools, plus DAW and browser components. Check the relevant repository's license and expect possible breaking changes while Studio remains early in development.

Where Specifiction places it

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