DeepSeek V4.1 Flash composed, synthesized and mixed a 3-minute synthwave track in pure browser code. No samples, no libraries, no audio files

I gave DeepSeek V4.1 Flash (max effort, in AgenC) one prompt: write an original synthwave track and build every sound from scratch with the browser's Web Audio API. What it made: - "Neon Tides": 3:22, 100 BPM, A minor, 84 bars in 8 sections (intro, verse, build, chorus, breakdown, second build, final chorus, outro), with chords written for each section - A lead melody built from one 2-bar motif that it repeats, varies and answers, plus a counter-melody in the last chorus - Every instrument synthesized from oscillators, noise and filters: kick, snare with a gated reverb tail, hats, clap, bass, chorused pads, a plucky arpeggio, a lead with vibrato and glide, risers, reverse cymbals and sub drops - A real mix: reverb made from a generated impulse, stereo delays, the pads and bass ducking under the kick, and a compressor and limiter on the master The exported WAV peaks at -2.3 dBFS with zero clipped samples. It's about 1,900 lines of JavaScript, with no libraries and no audio files anywhere. The page has Play/Stop, mute buttons per instrument, a live section readout, a "New variation" button that rewrites the melody and drum fills from a new seed, and a button that renders the whole song to a WAV in the browser. I'll put the full prompt in the first comment. Disclosure: I build AgenC ( github.com/tetsuo-ai/agenc-core ), and I'm a DeepSeek fan.