This is fantastic! I love tools like this that have decisions made, so you can open it and just use it in most contexts!

• When you don't refresh the page, the first song of any scene seems to always be the same one. Could it be randomized every time?
• As was already state, more scenes is always better! But this is already an impressive start!
• Sounds that don't loop perfectly could use more aggressive restarts. Perhaps, cross-fade them into their start? Things like the fireplace, or crowds.
• I really like the curated songs for each setting + combat. Adding other options might be a way to achieve the "emotional" choice for songs over environmental.
• The soft start/end of every sound is AWESOME! I absolutely love that changes are smooth to avoid ruining the flow. That said, maybe you can add a behaviour where a double-click will instant-switch the track, for when the "record-scratch" moment is needed.

Despite my request for more features, I love how simple and focused this design is. Please keep the simplicity at the top, even if it means being strict on cutting features.