What makes a good music producer?

What do rock, pop, and hip-hop music producers actually do?

For example, I can tell when bands like Tom Petty & The Heartbreakers of Red Hot Chilli Peppers are produced by Rick Rubin, but I can’t say why. What makes Rick Rubin a good producer?

My band is actually working with two different producers right now. This is the first time any of us have worked with a producer so we didn’t really know what to expect.
Both of the producers helped us A LOT with arrangement ideas, so the songs would stay interesting, and be formatted for radio. I think it is a producers job to know the trends of the style of music you are doing and know what will make your songs “radio ready”. I think the mark of a good producer is someone who manages to make your songs “radio ready”, while at the same time keeping in mind your sound, goals, and personality as a band, so that you come out of the project with a sound that is still your own, but ready for the radio. Then again, I don’t really know what I am talking about…

My husband’s old band worked with a producer, and the difference in quality was just amazing. He really had the ability to hear the song and help them come up with harmonies and arrangements that made the song more enjoyable to listen to as well as being more marketable. I think it’s really beneficial for a band to have a producer (if they’re trying to actually make it in the business) because a person not involved in the band can listen a lot more objectively.

That being said, however, I do know people who have worked with producers who totally changed the sound of their band. That is definitely not the hallmark of a good producer.

In the sense of trying to make a folk act into a heavy metal act I can see that. However many great albums have been made that involve a band changing it’s sound as the result of working with a particular producer (Brian Eno and Daniel Lanois come to mind).