Originally Posted by Deltadrummer
I always thought that was a guitar. :)
How much is bleeding also poor recording technique because I know a lot of bleeding was also on the vinyl?
Different kinds of bleeding.
'Bleed Through' is purely a process that occurs on old tape or tape that has been stored incorrectly. Essentially, the magnetic particles on one side of the tape affect the magnetic particles on the next reel around. So one layer magnetically alters another (because tape obviously is a series of differently charged miniature magnets). When tape is stored, it should actually be unwound and rewound on a reasonably regular basis - at least a couple of times a year - to prevent the magnetic fields from altering each other over time. That's just one example of incorrect treatment. The same can occur in cassettes to a much lesser extent. The accuracy of the transference between the layers can be remarkably clear and there is no way of editing out when remastering old tapes.
Bleed on recordings is microphone picking up another source during recording. A classic example would be a live recording where the guitar microphone (acoustic or amp) picks up some of the drum kit. This happened a lot more in the days of vinyl when bands were often playing live in the studio before individual multitracking became more popular.