How much of the soundtrack is diegetic?

Of course the characters' singing, the psalm cylinders, and the needolin music can all be heard by Hornet, but how much of the ambient music do we think she can hear? I personally believe that the Mist and Phantom soundtracks can be heard, since they're literally playing a pipe organ in universe. I also propose that most, if not all, of the background music in the Citadel is diegetic, since the Citadel bugs sing and have machines that produce music. The Bellhart and Verdania soundtracks could also be diegetic to some extent, since Bellhart (the song) features bells, as does Bellhart (the location), and Verdania (the song) features chimes, which can be found in the fountain/lake area of Verdania. What do y'all think?