At first listen, 'When the Levee Breaks' appears to be a fairly straight Led Zeppelin blues number, but repeat exposure reveals the track as one of the most complex studio creations the group ever recorded.

Inspired by the Great Mississippi Flood of 1927, 'When the Levee Breaks' was written and recorded by Kansas Joe McCoy and Memphis Minnie in 1929. Led Zeppelin recorded it for their untitled fourth album, closing out side two of the record with a bombastic version that centered around John Bonham's chugging drum track -- which he recorded in a stairwell to get the famous echo.

The track uses studio effects like backward echo, compression, flanging and altered tape speeds to achieve an effect that could almost be termed "orchestral blues" -- a natural for the Top 50 Led Zeppelin Songs.