The World itself:
The world of Shuffle is a patchwork sphere, everyone lives inside it, mostly in and around the Spire, a massive amalgamation of the cities of the world, twisting towards the center of the planet, where the "sun" is. The Spire is separated into "Tiers", The top, and most of the exterior of the tower is First Tier, Classical music reigns here, everything is soaked in it, to the point that nearly all the residents play, It's an almost orwellian society, lots of practicing, for perfect practice makes perfect....
Second Tier is the inside and lower levels of the Spire, a dark, neon lit realm with lots of police, but more personal freedoms than First. Turntables and mixers reign supreme here, Rave music, R&B, Rap, electonica, The stuff you'd expect in cities. Lastly, there's 3rd Tier, also known as Outside, the fringe, and other less than pleasant names. the further from the Spire, the more chaotic the Fringe is, sections of land from all around the world sewn together, dotted with settlements and radio stations. Most stations set up militias in order to protect their transmitter, as influence is power out here. The closer to the spire, the larger, and fewer, the stations. Around the Spire itself are three main stations, one being MMR. MMR has been rather benevolent as one of the big three, playing "Rock" music, not classic rock, not modern rock, or Alt, or any of the other flavors, but just rock, it's not uncommon to hear a brand new band after some Zepplin. MMR also runs the MMaRmy, originally their militia, but expanded to be almost the police force, stopping murders, people ripping off your gear, and generally being the awesome type of cops.
Next: leveling gear, spell scrolls, gig-combat, non-musician characters