Here’s the breakdown of GE requirements by college, which shows the close match between music and L&S (just 2 more courses in L&S):
The key thing to look at for double majors is the length of each. Double majoring in say politics and economics is easy, because both are short (12-14 courses). Geography is also short, but I think music is much longer (20 courses for the BA, I assume more for the BM?).
You do 3 or 4 courses a quarter, so with 10 GEs, you have about 30-38 left for major courses. You might just about fit 1 long and 1 short major into four years if you do 4 classes almost every quarter.
But BFAs/BMs are tough to do a double major/double degree. My D did a BFA in ballet and a BS in environmental studies (not at UCLA), and had to complete over 150 semester credits (ie 5 years of classes) in her 4 years with 20-22 credits almost every term.