The interior decorator model of positioning audio
The basic idea with panning and reverb is that you can create a room for your song to live in; a 3D space with specific objects in specific places, interacting with one another in specific ways. And you decorate that room like an interior designer, by placing objects intentionally in that space.
If you put your sound objects in random places that aren't super well thought-out, then your room might be kind of chaotic and stressful to be in, or it might cause imperceptible low-grade cognitive dissonance, and people might not want to spend a lot of time there, or to return much after an initial visit.
But if you take time to really think about what goes where, and what works well next to what, and if you take time to notice what interactions objects have when they're proximal to and existing alongside one another, then the room you design can be very pleasurable to be in, and it can make people want to spend more time there just purely because of how nice it is.
At a certain basic level, panning is how you position objects left to right, and reverb is how you move objects forward or back. By being precise in your settings, you can place objects very specifically within a 3D area, to create gorgeous spaces for your listeners to spend time in!
It really tied the room together — jamie