Volume controls

Just suppose you have a sound source in your living room, but would also like to enjoy your CD collection while you have breakfast. And on sunny days, your wife or girlfriend would also like to enjoy the same music while she sunbathes out on the patio. Different sound sources are not a must for you, but you would actually like to be able to individually control the zones where the music is playing. How do you do this? By means of a volume controller.