Piece of cake.
Players are independent agents that fetch their own music. A controller gives a player a list of things to do. At that point the controller and its hosting device can be shut down. Any controller can control any player and players can (optionally) be part of a "Group". All players in a Group, play the same tracks -- with individual room volume control if you like. Groups can be built or disbanded by any controller. Up to 32 controllers can be simultaneously active. Controllers can be any combination of Phone/Pad/Computer's. Mac/PC/Android/iOS are welcome.
Some users are vexed by the idea that any controller can control any player. This can result in some day one pranks, but since the prank capability is symmetric (If you prank me, there will be a payback), things settle down by day two after a truce is declared by all parties.