Does one have to be in all honors classes if they are applying to any of the University of California schools as a music major?
Not all “Honors” designated courses are UC approved. If you are attending a CA HS, you can look up which courses are UC approved for the extra honors points weighting here: https://hs-articulation.ucop.edu/agcourselist#/list/search/institution
That said UC’s expect applicants to take a rigorous course load based on what a HS offers. If your HS offers only a few Honors/AP’s than you should be fine.
Also if the UC music program is audition based, then your performance will weigh heavily into your application review.
Performance meaning music performance in an audition?
Yes.
Can you answer my other question about Duke 
@CheerBeluga: Unfortunately, I am not very familar with Duke. Hopefully other posters can chime in.
Ok, thank you for your help