@college12347 . . . the UCs don’t offer a General Studies degree. However, there are some that offer a design-one’s-own major. And I’m sure he’d have to have some elevated scholarly standing for this.
But then too per what @lkg4answers stated, he could go into an multi-interdisciplinary major like Cognitive Science. Cog Science is a good choice because it has elements of CS, psych, and other disciplines. Math and Economics might be a good major added to minors and specializations in programming/data science.
I don’t know if on all this one could attach a music minor, but he could explore various courses in music at the outset as breadth, or include them in his designed major.
I think it’s doable at UC, but more restrictive if he wanted pure CS because of this major’s heavy load.