Show HN: DJ Mix realtime local AI music with a controller; Magenta, Stable Audio

Notifications You must be signed in to change notification settings

Fork 0

Star 1

BranchesTags

Open more actions menu

Folders and files

NameName

Last commit message

Last commit date

Latest commit

History

216 Commits

216 Commits

.claude

.claude

backend

backend

docs

docs

frontend

frontend

.gitignore

.gitignore

CLAUDE.md

CLAUDE.md

README.md

README.md

justfile

justfile

Repository files navigation

Apple Silicon Mac (MLX backend)

uv

~13 GB disk for model weights (downloaded on first setup: Magenta ~4.5 GB for both deck models, Stable Audio 3 ~8 GB including the medium track model)

A Chromium-based browser (the app leans on Web Audio worklets and Web MIDI; it is developed and verified against Chrome)

Optional: a Pioneer DDJ-FLX4 for hardware control and its headphone jack

All common tasks live in the justfile — run just to list them.

Setup

just setup # backend deps, all model weights (~13 GB), frontend deps + build

Magenta models land in ~/Documents/Magenta/magenta-rt-v2 (override with MAGENTA_HOME): both deck models, the default mrt2_small and the heavier, higher-quality mrt2_base, selectable per deck in the UI — the app warns when the combined selection looks tight for your RAM. Stable Audio 3 — generated pads and tracks — is cloned to ~/Repos/stable-audio-3 (override with SA3_MLX_HOME; an existing checkout is reused) and its weights are pre-warmed so no request ever pays for a download; just setup-sa3 re-runs that half alone.

Run

just run

Then open http://127.0.0.1:8000 — add style targets to a deck's pad, hit play, blend targets by dragging the cursor (or the dots themselves, to cluster them), and ride the crossfader between decks.

Mixer — per-deck volume and Hi/Mid/Low EQ, crossfader, and Record, which captures the master bus to a downloadable WAV. The health row shows the stream buffer, underrun count, and generation speed.

Color FX — one knob per deck over a chosen effect: Filter (bipolar LPF/HPF), Dub Echo, Space, Crush, Noise, Sweep. The knob's centre/zero is a bit-exact bypass (ADR-0008).

Freeze loops — capture the last bars of a deck into one of four loop slots and hold the moment on air while you re-steer the model underneath; loops are session-only by design (ADR-0009).

Beat detection — each deck shows its detected BPM behind an honesty gate (a dash rather than a wrong number); with a confident tempo the Dub Echo syncs to the beat and freeze captures quantise to whole beats (ADR-0010).

Deck-to-deck style sampling — one press puts "the sound of the other deck, right now" on a deck's style pad as a blendable target; sampled targets are session-only by design (ADR-0011).

Crates — save a deck's pad + Color FX as a named preset, browse the crate from the FLX4's rotary, and load onto either deck mid-set; export/import as JSON for backup and sharing.

Master housekeeping — a limiter on the master (the meter, the recording, and the phones all hear the limited signal; its gain reduction shows in the mixer) and per-channel auto-gain Trim that levels decks of different loudness, with a manual override.

Headphone cue — hit a channel's Cue, ride the Cue mix knob between cue and master, and pick a Phones out: any output device the browser can reach, or the FLX4's own headphone jack, which is fed by the backend over USB (ADR-0007).

Settings (pad arrangements, volumes, crossfade) persist across reloads. Shortcuts: A/B focus a deck's style-target input, X focuses the crossfader.

For frontend development: just dev-backend in one terminal, just dev-frontend in another (the Vite dev server proxies /ws to the backend).

Hardware control (Pioneer DDJ-FLX4)

Plug in the FLX4 and click Connect MIDI (Chrome asks for MIDI with SysEx; plain MIDI works too, minus position sync). Mapped controls:

Play/pause, channel faders, three-band EQ, crossfader

Channel CUE buttons (headphone cue) and the transport CUE button (deck prep: prime a stopped deck off-air, stop a playing one)

SMART CFX knob — Color FX amount; hold SHIFT to sweep the style pad instead

PAD FX pad bank — select the deck's effect (re-press toggles it off); HOT CUE pads pick style targets; SAMPLER pads freeze loops (SHIFT + pad clears a slot)

HEADPHONES MIX knob — cue mix

Browse rotary + LOAD buttons — highlight a crate preset, load it onto deck 1 or 2

Knob and fader positions sync from the hardware on connect, and the LEDs mirror app state. The measured byte map lives in docs/midi-ddj-flx4.md.

Verify

just test — backend pytest + frontend vitest

just lint — format check, ruff, eslint, tsc

just check — both of the above; what a PR must pass

just verify-stream / just verify-ui — e2e against a running server (UI e2e needs Playwright Chromium once: npx playwright install chromium in frontend/)

just verify-worklets — the audio-worklet module graph loads in real Chromium (self-contained; jsdom executes none of the worklet code)

Hardware behaviour is verified by a human against the checklists in docs/ (m7-, m9-m10-, m12-hardware-checklist.md)

About

An AI DJ application

Resources

Readme

Uh oh!

There was an error while loading. Please reload this page.

Activity

Stars

1 star

Watchers

0 watching

Forks

0 forks

Report repository

Contributors

Uh oh!

There was an error while loading. Please reload this page.

Languages

TypeScript 69.4%

Python 14.8%

JavaScript 11.4%

CSS 3.9%

Other 0.5%