Babylon is the most famous live performance & concert hall in the area. You can enjoy world famous Turkish or foreign musicians here. Live music starts at 21:30 every day but closed on sundays and mondays. You can buy tickets online , (simply search "babylon" on this site) or at the entrance. Don't forget that tickets could be sold out days before for some performers.
Babylon is very closed to Refik Meyhanesi, just pass Refik and keep walking. It's in the first right street. You'll notice the crowd:)