DJ workstation — feature/dj_workstation

The main window now opens with the original karaoke workspace above a resizable DJ workspace. The toolbar’s Show/Hide DJ button returns the entire window to karaoke without stopping any deck. Existing singer, venue, rotation, video, background music, library and recursive directory import features remain available. Background music is a compact single-row strip above karaoke transport. In split view, song settings open from the Song Settings button; karaoke-only view keeps the full settings strip. DJ controls have mirrored tone panels, consistent padding and a separate browser area; the DJ workspace scrolls vertically when the split is too short to show everything.

Using the decks

Use the DJ browser’s Import Files / Folder button for DJ music. It has its own DJ/Library.sqlite, DJ/Media and playlists under the app support folder. It starts empty; existing karaoke songs are not migrated. The tested recursive importer is reused with audio-only import, without CDG graphics. MP3, WAV, M4A, MP4/M4V/MOV audio, AIFF/AIF, CAF, FLAC and AAC extensions are accepted; decoding depends on macOS format support. Imports support progress, cancellation and duplicate detection.
Select a DJ library row and use Load A/B, use the row’s A/B buttons, or drag a DJ library song onto a deck. Loading is paused, with no brief autoplay. Loading a playing deck replaces that track.
Cyan identifies A; amber identifies B. Each platter’s angle follows actual source playback time, including tempo changes, pauses and seeks. Drag around a platter to jog two source seconds per revolution. This is seek-based jogging, not vinyl scratching.
Waveforms come from decoded audio and reuse existing waveform caches. Click/drag to seek. A white position line and green loop region show current state.
High/mid/low EQ, bipolar filter, gain and level are beside each platter. Drag a knob vertically; double-click to reset. Knobs expose adjustable accessibility actions and current values. EQ uses the existing three-band filters; filter is low-pass left, bypass centre, high-pass right.
Play/pause, stop-to-start, set/return cue and four set/jump hot cues are per deck. Right-click a hot cue to clear it. Manual IN/OUT loops do not need BPM. Beat loops require confirmed BPM; choose 1–32 beats.
Enter source BPM (40–240) or tap at least three beats. Loading resets BPM to an unconfirmed placeholder. Sync matches the other deck’s effective tempo; it does not analyse BPM or align a beat grid. Use the jog/nudge buttons to align beats. Tempo adjustment preserves pitch, using AVAudioUnitTimePitch.
DJ master, channel levels and equal-power crossfader affect only DJ playback. The karaoke master and saved singer preferences are independent. The two meters show individual deck peaks, not a summed master meter. There is no master limiter; use gain/levels appropriately.
Karaoke and DJ music can play simultaneously. The existing background-to-singer interlock is preserved, but it does not automatically duck the new DJ decks.

Library and playlists

The DJ browser supports title/artist/album search and paginates in groups of 50. DJ playlists are stored independently from karaoke. Create, rename or delete them from the folder menu; right-click a song to add it to a playlist, remove it, or move it earlier/later. Karaoke library drag references are rejected by the DJ decks; import the source music using the DJ importer. DRM subscription streaming is not added.

Audio routing

The routing sheet enumerates CoreAudio output devices. Both DJ decks can route to one selected master device; karaoke can independently route to another device. Defaults use the system output. Selections are session-only. Background music retains its existing output.

Headphone preview is real, independent playback on another selected output device. It starts at the selected deck’s position with that deck’s current tempo/EQ/filter, before its gain, level and crossfader. Later deck changes are not followed; restart preview to refresh. One deck can be previewed at a time. Preview is disabled until an output is explicitly selected, and rejects the current master device to avoid sending cue audio publicly.

Not implemented: master/cue channel-pair selection on a single multichannel device, phase-locked PFL, aggregate-device creation, input/microphone routing, automatic device failover, and calibrated round-trip latency. Devices use their default stereo output pair. A Numark’s master and headphone sockets on the same CoreAudio device therefore cannot yet be independently addressed. Hardware routing needs verification on the intended interface.

Controllers

The user’s “Numark Mix Go” name is ambiguous. Numark documents DJ2GO, DJ2GO2 and DJ2GO2 Touch; DJ2GO2 Touch is class-compliant USB MIDI with an integrated audio interface. No exact model or physical unit has been confirmed.

Primary references:

Select the controller’s CoreMIDI input in MIDI Mapping, choose an action, click Learn Next Control, then press/move its hardware control. Mappings persist by source unique ID, channel, note/CC number; the learning gesture does not trigger playback. Select the source again after reconnecting. Note-off and zero-velocity note-on are ignored. CC zero remains valid for continuous controls. Relative signed and offset encoder modes apply only to Jog. Buttons, gain/EQ/filter/level/tempo, crossfader/master, cues/loop/sync/headphones and loading the selected browser row can be mapped.

Not implemented: factory mappings, controller certification, LED/output feedback, motor feedback, 14-bit controls, pitch bend mapping, HID/vendor handshakes or touch scratching. The implementation receives standard MIDI 1.0 notes and 7-bit CCs, with running-status, packet splitting, realtime and SysEx handling. MIDI source presence is discovered through CoreMIDI; automated tests exercise message decoding/learning/persistence and a real virtual CoreMIDI source with multiple packets, not a connected Numark.

Verification — 5 November 2026

Xcode 27.2 Debug build compiled for arm64 and x86_64, without distribution signing.
Full macOS XCTest suite: 113 tests, zero failures on Apple silicon. Intel compilation was verified; Intel runtime playback was not exercised.
Added checks for crossfader power/limits, tempo matching validation, paused load, mixer isolation, tapped BPM and beat loops, simultaneous real audio rendering, MIDI running status/realtime/SysEx/packet splitting, mapping persistence/button releases, real virtual CoreMIDI source delivery, and independent recursive DJ imports/playlists/reopening/deduplication.
Existing karaoke rotation, singer navigation, recursive CDG/audio import, background handoff/fades and offline EQ processing tests passed. Fixed-coordinate rotation UI tests were updated for the background strip’s new position.
Captured and visually inspected the actual NSHostingView macOS interface at 1320 × 1100 points, with separate karaoke and DJ fixture records and loaded background audio. This is a native app capture, not the HTML design preview.
Physical Numark controls, controller LEDs and separate physical audio outputs have not been exercised. Same-device master/cue channel pairs are not implemented. BPM/beat grids are not automatically analysed, and loops/jogs use seek scheduling rather than sample-accurate scratching.

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