in the extension there is a Hold Music selection option, i don't think there is a tenant-wide setting as far as I am aware, unless someone else can chime in
I just looked and there is a dialplan *9664 that you could edit I guess, so its tenant wide - but I have not tested this
if you want to change park music, you will need to edit the valet_park dial plan:
valet_hold_music=local_stream://tennant.domain.ca/whatyoucalledit
update, also see my post here
https://www.pbxforums.com/threads/custom-hold-music-oddity.6992/#post-28675 this worked for me with some custom hold music issues I was having