Show HN: Octave Compass – Svelte/TypeScript app to explore scales and chords

Author here. I built this interactive calculator-like tool for musical scales and the chords they contain. (Some understanding of music theory will be helpful when using it.) You can play it like an instrument set to play only the notes from one scale. Try pressing three (or four!) notes together to see what chord they form. Go to "Scale Editor" to set up your scale by transposing, mode-shifting, or toggling intervals to make it new scale. It will tell you the name of almost any set of intervals (scale or chord) — and it knows over 1,000 names! See "Scale Index" for the full list. The source code (GPL) is linked within "FAQ". Enjoy!