<p>I do think that Music Theory can hit even accomplished musicians as a shock. And it is not necessarily the whole class, but parts of it.</p>
<p>I think the ear training is hard for many. Also, the studies of chords structures and moving harmony, which are very math-like.</p>
<p>Instrumentalists may have an easier time than pure vocalists. Keyboard players may do better because they are accustomed to playing chords, not just melodies, as a normal function of their instrument. Jazz players can have an advantage because they often have an advanced understanding of chord structures and a good ear.</p>