One of the things I like most of visual-kei is the lack of professional quality of anything for many many bands--artwork, costume design, marketing, and recording quality. I love trying out bands' super early work that only came in tape form; some of my favorite works have never been re-recorded and shall forever live on in a muddled, hissing, tape.
So, what are your favorites? I'll try to post videos, but a lot of them I'm going to have to upload myself eventually since Youtube doesn't have everything. Oh, and feel free to not be restricted to just Japanese music.
+Crack Brain- 砂時計: love the melody of this one, and the poor quality adds an extra layer of creepy to it that I really enjoy. Unfortunately, this was never rerecorded (as far as I know).
+Luna Sea- Shade: I liked the demo version of this song more than the 1991 rerecording. Haven't heard the 2011 version yet, but I don't think it'll really do the same for me.
+Werkmare - Psychopass: Messy metal demo-tapes are fun. This one also has some Bach thrown in as well, which is always an added bonus. I'm actually reallly disappointed that this one wasn't rerecorded for real.
+Malice Mizer- Sans Logique: This tape is great. I really love their 2nd attempt at 'Speed of Desperate' and '終幕への扉' is pretty magical. Had this not be lo-fi, I probably would not have liked it as much.
+Madeth Gray'll- 狂死楽園: Ooky-spooky demos at their best. The recent version uploaded here also has some warping in the tape that make it sound so so much better, like an old horror movie. They also had like 100000 other demo tapes of similar quality that were all eventually re-recorded (multiple times, actually). This video isn't as warped as I had mentioned, but you'll get the point.