There will be more music added in future Acts, so the soundtrack hasn't been released so far. Once it's all done it will definitely be available for purchase though! Thanks for your interest!
We considered making a short spin-off that focuses more on Sappho, but as we're still working on the main game and other projects, we don't have any concrete plans for it.
We're glad you're enjoying the game though, and hope you'll like the future Acts as well!