They would be 100% wrong!
You don't have to be a music professor by any means when making rap beats, but you should have a basic understanding of how notes fit together in scales and how scales help you make chords and melodies. This will separate the average beat maker from the professional beat maker.
Don't be afraid of this. It is really pretty easy when you learn the basics of music theory.
It will make your rap beats much better because you will learn how to add extra musical elements like a bass line or melody.
Even if you are a sample based beat maker, you should understand these basic concepts. You will be able to blend more samples together and have them sound nice. You are trying to make music beats not random sounds thrown into a mix.
Many rap beat makers who are predominantly sample based add these extra elements to separate themselves from the crowd. Names like Kanye West, Just Blaze and DJ Premier come to mind. They all can take a sample and layer it with composed parts when making beats to make beats that stand out from the rest. Look at the pros for inspiration on how to make beats.
