Interesting thing about this theme song is that the original only had 6-8 people in it. They were all multi-Intrumentalists, and they got very creative in the studio to bring this about. I don't know if Ennio Morricone himself was in the studio or not, but whoever was in charge of this did an amazing job on the original. Sounds better here with a fuller orchestra, but the original was great, and is possibly the greatest theme song for a western movie of all time.
Also, the middle part of this theme song has been split off into its own and is called the "Ecstasy of Gold", also part of the same movie.
For a wider look at Ennio Morricone's spaghetti western music, see this:
Its long, but they are the orignal versions of the songs. Also, the female opera singer (Edda Dell'Orso) has an amazing voice, and is on a number of the songs.
P.S. For those who are familiar with early 1970s progressive rock, the song in the Ennio Morricone compilation called "For a Few Dollars More" is the basis for Babe Ruth's song "The Mexican".