I recently bought two tapes: Gush from 1990 (at least that's the year of release) is very good, as has been stated in this thread already. Riutalistic, dark, suffocating lo-fi atmosphere. Undersong from 1987 is not as good, but this is partly due to the crappy sound quality. I don't know if my copy was just badly dubbed, but it sounds really weak and bassy, with a lot of details being lost or just barely audible. Apart from this, the music is similarly dark as Gush, but more rhythmic at times with some ritualistic drumming here and there. Some tracks are not too exciting, like the final track on side B during which not much happens, but it goes on for nearly 15 minutes. Still, I don't regret buying the tape.
I also bought the My Candle Has Died LP, but haven't listened to it yet.
I'll have to look into buying Morbid Muppets and some other tapes, if they're affordable... And I'll have to get the first 7" too.
I wish Tanaka hadn't disappeared. I'd love to have a reissue of S·Core tapes on CD or vinyl.