There was a time when customer support meant you told a shop owner your issue with what they sold you, and they either decided the problem was for them to fix or your own damn fault. But then the telephone was invented and everything changed. Call centers emerged, phone trees were born, and suddenly there was no way around pressing '1' for one thing and '2' for another. It's actually pretty interesting stuff.
So when you find yourself wondering how on earth hold music came to be, and why it always seem to be smooth jazz, let this little history lesson fill in some of the blanks.