Matt Mazur

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 shape the rippling water. The scene gradually shifts from moonlight to dawn. It drew the animation frame by frame with Pillow and NumPy, then piped the frames into FFmpeg to encode a 720p video with audio. I asked for alternatives to the synthesized MIDI sound. It found Apple's built-in instrument bank on my Mac and wrote a Swift renderer using AVAudioEngine to render the concerto with sampled piano, strings, and cello, adding stereo placement and hall reverb. Finally, it used FFmpeg to swap in the new soundtrack without re-encoding the visuals, preserving the synchronization. This took four short prompts and about five minutes from start to finish. Here is the final video: