We have all experienced it: when put on hold you are made to suffer the most terrible muzak. This is not an invention of the electronic age.
Here is the mother of that method of torture. It is a music box from the 70s. You are supposed to put the handset on it, if you want to put somebody on hold. Then it starts to play the theme from the movie Dr. Shivago.
Those rings with numbers on it are a calendar. So you can keep track for how many days you have put someone on hold.