Signing in gives you one library across every Sonyk you use. Songs you push to the cloud appear on your phone, your Mac, the web and the headset, and every push keeps a restorable version, so a bad idea at 2am is never permanent.

Together

Invite someone to a song and you both work on the same material — the engine state itself is the format, so what you hear is what they hear. Invitations are claimed on sign-in, so you can invite someone who hasn't made an account yet.