ShoreTel was a Sunnyvale IP-phone company. Mitel bought it in 2017. Its systems shipped with a built-in stock music-on-hold track, and uploading your own WAV files through ShoreTel Director arrived around release 13.
The mystery
We found plenty of evidence that the stock track exists and none that names it. If you know the title, or you have the file from an old ShoreTel install, tell us. This is exactly the kind of thing this page exists to pin down.