I told Codex to "compose a concerto" using GPT-6 Astra just to see what would happen. It composed "Lanterns at the Water", a three-movement miniature concerto for piano and string orchestra, and generated MIDI, editable MusicXML scores, and a synthesized audio preview. I asked for a creative visualization and a video to accompany the audio. It wrote a Python renderer that reads the score: piano notes release floating lanterns, pitch determines their horizontal position, and sustained strings…