Thanks for the suggestion! To be honest I sometimes forget which sigil I picked too, and there is currently no way to check once you're underground, aside from Fortitude and Shield sigils since they show a buff counter. Instead of a tooltip, I think it might be more helpful to display the selected sigil as an icon next to the consumable slots or something. That way, even underground you can quickly see which sigil you have equipped.
As for the music, I am really glad you are enjoying it. I do plan to add more in the future, but the main concern right now is the file size. I try to keep Serenitrove as lightweight as possible. The entire game, including images and code, is only about 2.6 MB, while the 10 gramophone tracks alone take up around 24 MB.