IntervalKit

Project intro

IntervalKit is a guitar scale and chord laboratory for musicians — pick an instrument (guitar, mandolin, piano and more), choose a root note and a scale, and it lays out every fingering on the fretboard, plus the harmony built on each scale degree and ready-made chord palettes to jam with. In the author's own words: "This started out as a vibe-coded guitar scale fingering chart generator, and has gotten a little out of control." The "out of control" part is the good stuff: a Key Explorer that builds every possible 12-note chord from your selected intervals, and an Interval Chart comparing all scales against all tonal centers so you can find, say, the darkest scale in your key in seconds. It's the kind of obsessive music-theory toy that usually only exists as a spreadsheet — except this one is beautiful, interactive, and was built by a web developer who "likes to make useful things and experiment." Free, no signup, runs in the browser. A genuinely useful practice tool for guitarists and composers — and a fun example of what happens when a musician points an AI coding agent at their own itch.