I Built a DJ Playlist Optimizer Without Writing a Single Line of Code Myself

I'm not a programmer. I run a YouTube channel about electronic music (634K subs) and I DJ psytrance. I built a web app that solves a real problem I kept running into. Here's what happened. The Problem Every DJ using Rekordbox (in my case) knows this: you can sort playlists by key OR by BPM, but not both. And the key sort is alphabetical - A, Ab, Am, B — which has nothing to do with harmonic compatibility. Pioneer's own forum has a feature request for this sitting there for years. With 20 tracks, there are 2.4 quintillion possible orderings. No one's doing that by hand. What I Built HarmonySet — upload your Rekordbox playlist (.txt), get the mathematically optimal track order for harmonic mixing and energy flow (Serato and Traktor coming soon). The algorithm: Calculates harmonic distance between every track pair using the circle of fifths Solves it as a Traveling Salesman Problem (Held-Karp DP for ≤20 tracks, greedy + 2-opt for larger) Three energy modes: Ramp Up, Ramp Down, Wave Runs c