Every melody on Beepdex came from two parents. When you vote you choose which 8-bit tunes get to breed next — no model sits behind it, and nothing is hidden.
Each tune is a plain genome: key, scale, tempo, a chord progression, a melody, and a bassline. A boldness gene (0.0–1.0) sets how daring it gets, and melody and bass are both locked to the chord progression so even random mutations stay in tune.
When you tap a tune it wins, and winners get chosen as parents more often — that vote is the only signal the engine runs on. Parenting uses a Laplace-smoothed win rate, while survival uses a stricter measure: the same votes seen through two lenses.
Beepdex keeps the best tune in each of 125 niches instead of hunting for one perfect song. The MAP-Elites archive is 3 perceptual axes (brightness, energy, character) × 5 bands = 125 cells, so a gloomy banger and a sunny banger can both win forever.
A batch fires every 24 hours or every 50 votes, whichever comes first. Two popular tunes are chosen by tournament selection and combined with a bar-aligned single-point crossover, then nudged with note-level mutations — staying in key by construction, not by luck.
A newborn can knock out the tune holding its niche only if that elite has not proven itself yet. The sitting elite is judged by the Wilson score lower bound of its win rate; if that bound is at or above 0.5 it is protected, so luck never beats evidence.
When a niche goes quiet for 3 generations and its elite is unproven, it becomes a zombie cell and Beepdex seeds fresh genes into it. The rescue is non-destructive: a near-miss colonizes only an empty cell and proven elites are never bulldozed, so no corner of the map dies.
No model was trained on anyone’s music, so every tune is CC0: download, sell, or remix it with no credit required. The genes are plain notes you can read, and the deliberate 8-bit limit keeps Beepdex out of the audio-quality arms race for good. It is a glass box.