I hate to agree with those that say a bass player who plays guitar is a bad thing as I do both. But I am naturally a bassist. I hear that rhythm first, and the melody second and find myself more on the beat than on the melody. I once was trying to tell a friend about a song and told him it went like this and proceeded to sing the bass line and drum rhythm for him. He gave me a weird look but got it. Bass has always felt more natural to me.