XM satellite radio receiver on a Ram mount hard wired to bike.
Output from XM receiver into an on/off toggle switch mounted in the front edge of the tank bag so if your buddy wants to say something at a stop light you can switch off the music and hear him, turn it on and down the road you go. This on/off switch will need six terminals, right left and ground, 3 for in and 3 for out (amazon) and a water proof boot over the toggle.
From the on/off switch into a Boosteroo amp in the tank bag.
From Boosteroo output to a connector to plug ear buds into that clips on the edge of the tank bag for easy access to plug in ear buds to get off the bike. You can plug the ear buds directly into the Boostaroo if you want. The Boostaroo turns on and off by plugging in the input wire.
Koss ear buds with volume control, earplugs and music all in one, Walmart less than $30, easy volume control is a must.
I wear a scull cap to keep the helmet from pulling the ear buds out when you put on the helmet.
The boosteroo uses AAAA batteries and will last two weeks of all day riding
. This set up takes a bit of time to put together but doesn't cost much except for the XM subscription and receiver. It is portable so I can easily put it in the truck for road trips.