Lunar Threads

It would have been incredible if Somoga actually included the Sega CD soundtrack in the retro mode option like in this game video that turned out excellent

It's a lot more complicated than just doing a one-to-one swap of TSS's and SSS's music tracks. There are a lot more tracks in SSS, and the BGM frequently changes during sprite scenes in ways that would sound weird with the TSS music. Example: In the scene after Tempest's anime intro, at some point the music changes to Solitary Wolf, which is the Pao town music as well as Tempest's music. In TSS, Pao doesn't have its own music; it's the same as Lann and Lyton. Having that rather peaceful village music suddenly start while Tempest is being all combative would be pretty jarring. And this sort of thing is the case for many scenes, where there just isn't really an appropriate TSS track to fit the SSS scene.