# Mixtape

- **Event:** [GPT-6 Astra Hackathon NYC](https://cerebralvalley.ai/e/openai-gpt-6-astra-nyc)
- **When:** Thu, Sep 10 at 9:00 AM – 10:00 PM (EDT)
- **Where:** New York, NY
- **Placement:** Finalist
- **Team:** [Andrew Smith](https://cerebralvalley.ai/u/andrewsmith)
- **GitHub:** https://github.com/our-mixtape/the-booth
- **Demo video:** https://www.loom.com/share/8527fbed85454cfdba2e1aff4309a630
- **Gallery:** https://cerebralvalley.ai/e/openai-gpt-6-astra-nyc/hackathon/gallery
- **Page:** https://cerebralvalley.ai/e/openai-gpt-6-astra-nyc/hackathon/gallery/41

Mixtape — The Booth is a DJ instrument you perform in, built in the browser with Web Audio and Three.js. Two CDJ-style players or two turntables share one live mix, and switching rigs mid-set keeps every track, blend and stem exactly where it was. A practice exercise scores one real skill, bringing the second track in on bar five and owning it by bar nine, then restores the exact starting point so you can try again.

GPT-6 Astra is the companion behind the decks. It never hears audio. It reads the instrument's measured state, positions, tempo with provenance, gains, filter, EQ, stem routing and your last eight moves, and answers through the Responses API with strict Structured Outputs: one grounded observation, one next action. Change the brief and the plan changes. The domain layer rejects every model command, so your hands stay authoritative.

Built with Codex on GPT-6 Astra, including a Blender-authored mixer wired to live audio and a test suite that caught timing bugs the tolerance refused to forgive.

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Markdown version of https://cerebralvalley.ai/e/openai-gpt-6-astra-nyc/hackathon/gallery/41. Site index for agents: https://cerebralvalley.ai/llms.txt · full text: https://cerebralvalley.ai/llms-full.txt