One 3K-word prompt, 4 hours: agent builds a 2-minute Blender+MIDI music video end to end

mika314 · reddit · 2026-10-09

A production experiment: the author gave "GPT-6 Astra Ultra" a single 2,778-word production prompt and let it run about four hours unsupervised, producing Leave a Way — a 2-minute Eurodance song and Blender video.

No media-generation models: music was explicitly scored at 128 BPM with MIDI, conventional synthesis/DSP, and seven drum/piano/Foley samples; visuals came from scripted Blender scenes (eight-leaf folding mechanism, a bead, a broken track, in-world lyrics) with asset-pack props.
In-run iteration: the agent dropped drums and bass for six bars at the story's decision point, fixed intersecting geometry, adjusted camera framing, and aligned lyric visibility to sung phonemes. "One-shot" means one initial instruction, not one attempt.
Automated checks: it wrote checks for vocal pitch/timing, clipping and loudness, stem reconstruction, text framing, contact clearance, and video decoding; both exports were 120s/3,600 frames with identical soundtracks. The author notes these establish technical properties, not taste or storytelling quality.
Key design choice: upfront specification of editable deliverables (Blender scenes, MIDI, stems, source scripts) and checkable constraints made decisions inspectable. Disclosure: local DiffSinger supplied vocals, Gemma 3 1B and Llama 3 8B helped brainstorm; with existing tools and assets, this is a single production example, not a benchmark.

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One 3K-word prompt, 4 hours: agent builds a 2-minute Blender+MIDI music video end to end

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