OpenMixing

An MCP server (stdio) that lets an agent DJ a folder of tracks. Open your agent in the tracks folder, call the tools, and build a set: a timeline of deck clips with EQ, DJ filter, volume, tempo, tempo-synced fx and loops. render mixes it offline to FLAC/WAV/MP3; the web UI (open_player) only plays the result.

Install

python -m venv .venv && .venv/bin/pip install -e .[dev]
# optional: .[stems] (Demucs stem separation, pulls torch), .[beat] (beat_this beat tracking), .[fingerprint] (AcoustID); ffmpeg is needed for LUFS/true-peak and mp3

Related MCP server: messier-live

MCP config (run from the tracks folder)

{"mcpServers": {"openmixing": {"command": "/path/to/OpenMixing/.venv/bin/python", "args": ["-m", "openmixing"]}}}

State lives in ./.openmixing/ (analysis cache, sets, renders). The agent playbook is served as the openmixing://guide resource and the dj_set prompt.

Tools

• Library / analysis: list_tracks, analyze_track (bpm, beat grid, downbeat, key/Camelot, loudness, energy, sections, mix points, loop candidates, tags), analyze_all, lookup_online (MusicBrainz, Deezer, iTunes, ReccoBeats; Last.fm / Discogs / AcoustID with API keys), override_track, set_cue / list_cues / delete_cue, find_tracks, compare_tracks, suggest_next, suggest_order

• Stems: separate_stems (Demucs htdemucs -> vocals / drums / bass / other with a per-stem quality report, cached in .openmixing/stems/), then add_clip / edit_clip with stems=True, set_stem per-stem faders and stem_preset (instrumental / acapella / drumless / bassless); apply_transition style stem_blend

• Tags / files: set_tags (title, artist, album, genre, year, comment, label, isrc, rating, color, tags, notes; sidecar by default, write_to_file=True opts in to writing the file after a backup), check_files (format report per file; MP3, FLAC, WAV, AIFF, AAC/M4A, OGG, Opus), export_tracklist (text / json / cue)

• Sets: list_sets, new_set, open_set, get_set, add_clip, edit_clip, remove_clip

• Mixer: set_eq (low/mid/high, down to kill), set_filter, set_volume, crossfade, set_tempo, sync_clip, clear_automation, apply_transition (bass_swap, long_blend, filter_fade, echo_out, drop_swap, loop_roll_out)

• FX / loops: list_fx, add_fx (optionally stem= to hit one stem only), remove_fx, add_loop, remove_loop, at 1/16, 1/8, 1/4, 1/2, 1, 2, 4, 8, 16, 32 beats

• Transition planning: find_windows (exit / entry regions), pair_report (tempo, key, loudness, bass / vocal overlap, phrase, each with confidence), suggest_transitions (ranked candidates with sub-scores, plan documents, infeasible reasons)

• Plans: get_plan_schema, validate_plan, apply_plan (atomic, dry_run), export_plan: describe a whole set as one versioned JSON document

• Output: audit_set, render, preview_transition, open_player, project_info

• Discovery / detail: capabilities (formats, stems, fx, styles, curves, optional deps, versions), get_region (energy, bass, onsets, vocal, beats, sections, loops, cues, waveform for a range of bars)

Track ids are content hashes, so renaming or moving a file keeps its analysis. Positions accept bars, "64 beats", "95.5s", "cue:<name>" and "section:<label>+N". Tool errors come back as {error: {code, field, message, fix}}. Every render includes a validation block (low-end overlap per deck, intent report, clipping, unplanned silence, beat drift in ms, loudness jump across overlaps). Every analysis estimate has a confidence (0..1) and confidence_components; responses carry a versions block. Files are read only inside the tracks folder and written only inside .openmixing/ (the one exception is set_tags(write_to_file=True), which edits the tags of the audio file you name, after a backup) (path_not_allowed otherwise). render_variations renders distinct takes of a transition and compare_renders diffs two. Plans can declare an intent. See CHECKLIST.md for the roadmap.

Section boundaries are snapped to the 4-bar grid (raw_start_bar keeps the detected bar). When Demucs leaves the bass stem empty (808 music), the low end is treated as living in the drums stem: effective(...)["bass_carrier"] reports "drums_lowband".

See stage-1-testing.md for a manual test guide.

License

GPL-3.0-or-later, see LICENSE.

Limitations

Downbeat detection is a kick-energy heuristic; Last.fm/Discogs/AcoustID paths are untested without keys; no vocal detection; Serato crate/marker import is not implemented.