In the olden days of my youth, doorbells were hard-wired into the house's electrical system. Something you couldn't do or have done to a rental unit. Well, unless you had a really nice landlord and wanted to leave your chimes when you moved. Not a good solution.

Today, battery-powered units offer more than 10 different tunes, play different sounds or songs for each door, and have sound quality so good you can actually recognize the song. There are even options to add receivers in other rooms. After all, a doorbell isn't much good if you don't hear it.