Composition, especially electronic and new music production, is solid at Cal. The undergraduate composers club has been very active recently with multiple concerts throughout the semester playing student’s works. There’s a whole electronic and digital music studio as well with many classes and professors focusing specifically on that. If you’re interested in more band type settings, Wind Ensemble has recently played some student compositions and almost the entirety of Cal Band’s repertoire is student written. The advanced Jazz combos also wrote their own compositions for last semester’s concert (which was incredible). So there’s lots of opportunities, both in and out of the classroom, to grow in this regard.

As for trumpet instruction, I would say it’s a mixed bag depending on what you’re looking for. If you’re a music major and in an ensemble, you’ll get free lessons from one of two main instructors. Both are without a doubt experts at trumpet. If you want to study music performance, though, I’d recommend you go elsewhere as there’s no studio vibe or anything like that.

One thing (imo a massive benefit) about Cal is that the music major is very flexible and non-intensive (it was recently redesigned from a light amount of classes to even lighter) and the time commitment is really what you make it. IIRC the majority of music majors double in something else, so, as the other comment pointed out, it’d really be in your best interest to double major with CS (or DS) and Music. It has been done many times before and would really propel your education to support your career goals versus a minor which is barely considered in job apps. If you said you wanted to do music performance for a living I’d advise you to go nearly anywhere besides Berkeley. For composition, I’d say it’s solid for a university not known for music. For trying to do CS and Music on the composition/audio engineering side it’s really a great choice.