What are the requirements needed to become a musician?

You can major in music at a four-year college and get your B.M (Bachelor of Music degree). You'll have to take courses such as Music Fundamentals, Music Theory, stuff like that. And depending on what type of musician you want to be you'll have to take lessons (i.e. piano/guitar/vocal) In addition to that you'll probably have to take sight-reading/sight-singing classes.