Re: weird overdubs
It's actually true, indeed. Tape does have a tendency to deteriorate and there was a particular period when the tape being made by (3M I think) one company actually had a manufacturing flaw that meant that it deteriorated particularly quickly. I think one of the glue layers had a flaw and it meant there was separation between them. Those tapes had to actually be baked in an oven to be playable and then they would only work a couple of times - so quite a lot of tape has actually been lost and vinyl mastering has been the only option.
A lot of really old records (think Django, etc) were actually cut straight to vinyl - which is fascinating to me - and it wasn't until the mid-50's until tape started taking over as it was far more reliable. Until then, the tape was far too crude and inconsistent.
Going full circle, the band Portishead's second album (Called Portishead) went through and interesting mastering process, making heavy use of vinyl. If I recall correctly, they mastered to tape, then mastered to vinyl and then mastered back to tape from the vinyl - so if you listen to the record, it has a dark, grainy characteristic. It sounds great - but not something I'd use all the time. The album is incredibly dark; so it works.