I keep hearing about these statements that "a hard drive is like a cassette tape because it is a magnetic medium". That got me thinking...
Back in the day when I used to play DJ as a young lad, I would record music off the radio while played as the announcer to each song. Sometimes I would mess up and would have to rerecord of the flubbed portion of the tape, and upon reviewing, there was a noticable quatlity difference. Later in life I would learn that quality difference came from the fact the of the previous recording still existed on the tape, at least enough to distort the sound. It's the same idea as bending a steel fork or spoon; if you bend it and then bend it back, you will always have a small indentation where the original bend had occured.
Does this characteristic exist in magnetic base hard drives, and if so, is it detectable? Please consider the scenario that it has only been overwritten once.