spaghetti

Recently some interesting spaghetti westerns have come to dvd.
Often they include both the English as the Italian version.

I was checking which one was the original by looking what version was
lip-synch. Well, often the main characters are sync in English, but
smaller characters are either sync in Italian or not sync at all.
But what I did discover that sometimes the Italian mix sounded more
genuine and better acted.
For instance with Django Kill. I even noticed that at the part I was
checking the dvd, the English version had music, where the Italian
version didn't.
How did this work? Did the Italian film makers only make the Italian
version of a western themselves? Did the American distributor make the
English dubbed versions?
Or did the Italians supervise the English version with the bad voice
actors themselves as well? And what's ip with this difference in the use
of music?

Martin