A bit more on the sequencer: it's not meant for composing full songs, it's a scratchpad for testing chord progressions. You can adjust tempo, time signature, and note length to hear how a progression feels at different speeds and rhythms.

If you change the scale or mode, you can. update the chords (click the update button) to reflect the new diatonic chords, so you can quickly A/B the same progression in, say, Ionian vs. Mixolydian.

I have some ideas for what to add next like for instance PDF export with chords or MIDI export, but I'd rather hear what would actually be useful to you. What would make this tool part of your workflow?