In 1962, inventor and entrepreneur Alfred Levy found a loose wire touching a metal girder at his factory. It amplified the broadcast signal from the radio station next door and transmitted the audio through the loose wire to calls on hold. Four years later he patented his work, and music on hold was born.
On-hold music is considered standard in business phone systems today because people actually perceived wait times as shorter when they hear it. On-hold music traditionally worked by having specialized equipment attached to the phone, and the jack might plug into the radio, then tapes, then CDs, then MP3 players. PRI boards are built with jacks to play on-hold music.

"Messages on hold are often one of the most painful of customer ordeals. But when done right by Scott Greggory and crew with actual humor, it takes a customer hassle and elevates it to a customer experience you tell others about. Click through to check out a couple samples. They're addictive, and brilliant marketing." - Bill Cusick / Author & Customer Experience Expert
How to Format Your On Hold Script. For an average IVR phone system where customers are on hold for 1-3 minutes, it’s wise to have at least two courtesy messages and two marketing messages, with each message timing out to precisely 30 seconds (:30). Hold music should play in between the messages for 30 seconds (:30).