Just popping in to say that kbbob is right, it's r1-99, r115, r160, r175 currently!

Melody items (115) were the most recent to be added. Coda Caves Gems were r150 and we changed them to r160 so they could be fraggable. :) and I are working on getting things in r150 to their proper rarities (like getting old melody items out of 150 or old game prizes) so you can frag them.