They are how you find music here, and that is all they are. Playback happens inside their own players, under their own terms, and their audio never reaches the effects chain, the recorder or any analysis. No downloading, no stream capture, no exceptions for the one song you really want.
Karaoke, stems, pitch correction and everything else apply only to audio the platform is permitted to process: your own recordings, tracks you hold the rights to, and licensed material. The rule is enforced by the type system rather than by good intentions — a function that processes audio will not compile against an external track reference.