Click the Settings Button on your dialer 
on the bottom left of your dialer.
Click the pencil icon 
underneath "MOH" then you can silence or set the hold music to what you prefer from here. When you have chosen the music, you prefer you will need to Save Changes.
Remember, when changing the hold music, you need to be logged in from the seat you are trying to run the dialer from. If changes do not take effect log out, then log back in for changes to take affect.
