Infringement of Copyrighted Songs?

I’m preparing for a Copyrights exam in less than 48 hours. One part of the test for copyright infringement asks whether the “ordinary observer” would find substantial similarity between the two works.

This video provides a good opportunity for you, as the ordinary observer, to decide whether songs are substantially similar to each other. There are several sets of provided, the original work followed by the allegedly infringing song.

The last one is the most trippy. You can hear the full version of Taurus by Spirit on this video:
http://www.youtube.com/watch?v=ogTFdlbup24 (embedding not allowed on this one.)

And here is a second set to provide your opinion as the “ordinary observer.”