Music Stems

Splits an already-generated production into vocals/drums/bass/other stems.

When to use

The user wants isolated stems from a track they've already generated (remixing, karaoke tracks, sampling). Needs an existing production id — run music-list first if you don't have one.

Steps

1. Call mcp__cogmusic__separate_stems({ id: "<production-id>" }). This is a real GPU job — it takes real time, similar order of magnitude to generation itself, and shares the same underlying inference service as create_production (see the reliability notes in music-generate's SKILL.md — a transient failure is worth one retry before concluding something's wrong).
2. This does not return audio. The result only confirms which stems were produced. Check has_stems via mcp__cogmusic__get_production afterward, then point the user at the dashboard (music.cognitum.one) to actually listen — per ADR-0001, the current cogmusic MCP tool surface doesn't expose a stem-level audio_url the way the primary production audio has one (only the main track's URL is PAT-authorized today).
3. If the user specifically needs the stem bytes delivered back through this session rather than via the dashboard, say so plainly — that's a real gap in the current MCP surface, not something this skill can work around.