Thank you for the nice review!
The music/sfx is something that is always a hole for me... For the same reason I stick to ASCII, trying to build _good_ music and sfx is really non-trivial, much like trying to build good tiles. You want it to reflect the game itself, not just be generic, which requires serious composing skills... (My composing is worse than my art, and if you've seen the classic POWDER tiles, you'll know the state of my art ability :>) SFX is also pretty hard to build into a roguelike as they are meant to allow extremely rapid fire turns. Ambient music is definitely more approachable though.
I am glad you liked the twilight. It is always shocking how something simple like that can really add atmosphere. Though thanks to night, I needed lighting on the surface world, which meant that forest fires would kill system performance, forcing more rounds of optimization... :> But that is what I always like about developing during a 7DRL. I get to see how the game takes itself beyond my original plans and vision.