had followed this posting since the begining,
here are my findings:
http://www.vocalist.org.uk/music_producers.html
http://www.music-tech.com/business.php?subaction=showfull&id=1112852305&archive=&start_from=&ucat=2&
Here is a reply of mine to a person who asked "how do you become a professional producer?".First of all, realize that there is a difference between a "producer" and an "engineer".
The producer is pretty much the creative director. He usually doesn't operate the equipment or anything like that. He's the one who helps guide the artists and tries to get the best performance possible from them. He may also make suggestions about song arrangements and overall sound, and will try to convey to the engineer the type of sound he wants. Producers don't necessarily need any formal background in audio engineering, although many of them are very capable audio engineers as well. They also don't necessarily have to have any musical training either, but they certainly need to have a good ear for music and be able to communicate with all the musicians, and so those with a good understanding of music and music theory tend to do a little bit better in general.
On the other hand, the engineer is usually just the technical guy who sets up and operates all the recording equipment, and is responsible for getting the best possible sound to tape. His job is to focus on things like proper signal level to make sure nothing is distorting or being recorded at too low of levels, make sure the gear is operating correctly, and to try to get the type of sound that the producer and artists want. He is the technical guy, although a musical background is also very helpful.
Now days, the line between producer and engineer has blurred quite a bit, and you'll often find one person doing both roles at the same time (I do this quite often). It can be tough to try to do both, to listen for the technical aspects as well as to concentrate on the performance and try to coach the artists, but many people do both jobs at the same time. Also, in many styles of music these days (especially rap/hip-hop, and electronic music) the "producer" is the person who also comes up with the music and/or beats. Even with your standard pop/rock bands, many producers will still contribute to the music on the albums and may play several parts themselves.