12tone's YouTube channel is amazing, especially his Building Blocks playlist: https://www.youtube.com/watch?v=xTOOWe_yLwY&list=PLMvVESrbjB...
I'm also working on Harmony Explorer - a CLI tool that lets you hear any chord. It's brilliant for seeing what a chord progression sounds like before taking the time to play it on your instrument of choice: https://github.com/tiniuclx/harmony-explorer