Trying to understand a bit better how the home audio components work together

I am trying to figure out how the audio components work together for whole house audio.

I have the monoprice 6 zone amp, and a NAS to store the music.

Controlling the amp, would control what source the music comes from, as well as the volumes. But how do I control the actual music playing?

If I have two different songs on the amp, and I want, one song to go to zone one and the other song to go to song two, how do I select that? And getting the audio from the NAS to the amp, does it go via regular audio in? If yes do I need multiple devices to be able to play two different songs at once?

Do I need a different integration installed?

Thank you

I have the mono amp as well, the integration basically allows you to do the same functions as the keypads ( turn on a zone, adjust volume, switch a source). I have 2 chrome cast audio devices plugged into 2 inputs as well as an airplay device plugged into another input. The chrome cast audio devices do show up in Home Assistant so I can see what’s playing but I cast to those devices from my Google Home.

In other words you need some device plugged into the inputs on your amp. The device would have to pull music from your server. There are some solutions out there that integrate with Home Assistant that can do that, but you might need to run it on a PI to make it all work. Is one such solution which I have seen in a YouTube Video that looks interesting.