There are many roles in the making of a music recording. From the sound engineer to the mastering engineer, a lot of people will have a hand in the final CD that you put in your player.
None however, is as important as the Producer.

A typical album recording usually starts with the Producer listening to all of the songs an artist has available for the album. The songs may already be "demo" recorded, or they maybe performed by the artist at regular live shows. If not, sessions will be arranged to map out the songs either in a small studio or in a rehearsal hall.
The Producers duty in choosing the songs is to satisfy, first, the artist, second the Record company, and third the public.
The next step would be to hire the sound engineer, and together with the artist, choose a recording studio that fits the atmosphere and budget of the project.

In the studio the Producer will handle all of the logistics including money requirments, while "directing" the musicians and the sound engineer to deliver the quality needed for the end result.
Helping the performers to attain their goals is how I think of it. Getting the best out of everyone involved. Being able to make the final decisions about the arrangments and sound styles is how the Producer earns his royalties.

Some Producers are known for their hands on approach to recording like Bob Ezrin, who has engineered and performed on numerous albums he has produced, namely Pink Floyds'The Wall.

David Foster is another musical Producer who has a direct hand in the songwriting as well as the performances on tape.

Rick Nowells is another songwriting Producer with great success in his field

George Martin played a lot of the keyboards and wrote many String and Brass arrangments for the Beatles in their day.

Chris Thomas can be heard playing the Harsichord on "Piggies" and the Meletron on "Bungalow Bill" on the White Album.

Artists have a habit of not mentioning the people they work with, unless of course the Producer is more famous than they are, as in the above mentioned!

Next time you are looking at an album cover, (you might need a magnifying glass!) look for the Producer and see if you can recognize the musical style they have brought to the Album.

I think of the record Producer as the film Director. And sometimes they become a part of the group in a way that is most important to the end result. What would U2 sound like without Brian Eno and Daniel Lanois?