A technical problem i had with my technics stereo cassette desk rs-5 where playback would deliver this fading squarewave at maximum volume. Apparently, it could have been an issue with the tape header wearing out. Thought i might as well upload it here, as i'm not sure anyone will be able to create this sound again. Note, this sound was de-amplifiied by 10 db in audacity 3. 1. 3. Simply put, the raw file was incredibly loud. If you're curious enough, you can increase it back up to its original volume, though i wouldn't advise it.
Author: Onekellyordered