As well as the quality being bad most of the time the actual music is awful as well.
I have noticed the hold music twice in the last week.
The first time the music quality and pick was okay, but every time it got to a certain really high note, there was a pause and the note repeated as though someone was pushing a number on the phone a few times.
The other time, the on hold stuff was too loud. It was definitely not a suitable pick for transmitting over the phone (because of the instruments used etc). And it definitely did not end up at my end as music. It was so awful I did hang up.