Harmony is usually taught as a list of rules: which degrees go with which, which cadence resolves where. That works for passing an exam and less well for writing, because what decides whether a progression moves you isn't that it follows the rule — it's how the step from one chord to the next sounds.
Chord Cosmos reverses the order. The chords sit in a ring where those sharing notes — and therefore sounding natural in sequence — end up near each other. You place chords on the track, loop it, and decide by ear. You end up recognising why certain combinations work before you know what they're called.
Switching instrument isn't decoration: the same progression occupies a different region of the spectrum depending on what plays it, and that changes what room is left for everything else. A chord on piano fills the mids; the same chord on a pad spreads out and competes with the vocal. Switching while it loops is the fastest way to notice.
No. The ring places chords so that neighbours sound good in sequence, so you can build progressions that work without knowing their names. The name comes later, if you're interested.
Free and no sign-up, in the browser. There's no paid tier in this tool: it's an exploration space, not a game with progression.
Yes. The idea is that you take the progression to your DAW; what's trained here is the decision, and the real arrangement happens where you produce.
More than it seems. The same progression on piano occupies the mids and on a pad spreads until it competes with the vocal. Many problems people attack with EQ are really arrangement problems.
That relationship between timbre and available space governs an entire mix, and it's explained band by band — each zone playable — in the frequency ranges guide. As a reference to compare against by ear, there's the online piano. And if what you're after is chords arriving in tune to the mix, the tuning guide.