sabbath = band('metal', 'Black Sabbath')
sabbath.add_member('Ozzy Osbourne', 'lead vocals')
sabbath.add_member('Tony Iommi', 'guitar')
sabbath.add_member('Geezer Butler', 'bass')
sabbath.add_member('Bill Ward', 'drums')

zeppelin = band('rock', 'Led Zeppelin')
zeppelin.add_member('Robert Plant', 'vocals')
zeppelin.add_member('Jimmy Page', 'guitar')
zeppelin.add_member('John Paul Jones', 'bass')
zeppelin.add_member('John Bonham', 'drums')

concert = {'8:30': 'Black Sabbath', '10:00': 'Led Zeppelin'}
