OST vs bgm (Some tracks missing from Psycho Pass OST)

[Trarc]

When companies release OST's, they don't always have all the bgm in the anime, like how the Ode to Joy music from Psycho Pass Episode 11 (~8:00) is not in the "Complete OST's Album."

Likewise there was a piano track I've been looking for in the later episodes that's not in the OST. I don't remember when it's played. Even if I did track down where the piece played, how would I find a complete list of bgms used in Psycho Pass? My searches have been coming up blank.

And just in general, what do companies usually do with bgms that aren't in the OSTs?