If you are talking about the Sonamp 12-50, it does not mute or duck anything. The dip switches tell the amp what inputs to use for those channels. You can select 1, 2, or 3 inputs to be active at the same time. At that point it is mixing the inputs.
So you can run doorbell audio into this (or paging audio) but it will just mix in with the music playing. You would have to use a separate ducking module for each source you wanted to mute when the doorbell rang or a page was happening. Unless you just allow the music to keep playing thru.