Firstly, unless you are going to work with other musicians, you need musical ability. If you donâ€™t know an A-sharp from a Z-blunt, how are you going to create the music that is the producerâ€™s raw material.
Second, many excellent musicians canâ€™t play a note that someone else hasn't played before. In addition to having musical ability, you need to be musically inventive.
Third, you need a great ear for sound. If you were a great musician and were musically inventive, you might be able to put on a great live show. But that doesn't mean you can make a great recording. Skill with sound is something very different from skill with music, and you need both.
Finally you need the technical ability to put it all together. Knowledge and skills with EQ, compressors, mixing, mastering etc.
Oh, and to become a successful producer, you will have to be able to sell yourself too. Now that's something else entirely…