The best hold music I ever heard...
...was a large music shop in Birmingham that had it's own tech music studio.
The hold music was unsigned artists demo's.
After being on hold for 5 minutes someone answered and I asked to be put back on hold, which he happily did. Once the track finished, he picked up again. I sort of apologised, admitting i really liked the track at which point he said it was a common occurrence and occasionally they were asked to put people on hold until they hung up.