Conversation so far:
Where was Phil Lesh born?
Phil Lesh was born in Berkeley, California.
What was significant about Phil Lesh's childhood?
Phil Lesh started out as a violin player.
Did Phil Lesh go to college?
Phil Lesh enrolled at the College of San Mateo.
Did Phil Lesh play violin in any orchestra in high school?
While enrolled at Berkeley High School, Phil Lesh switched to trumpet and participated in all of the school's music-related extracurricular activities.
What did Phil Lesh do after school?
Upon dropping out, Phil Lesh successfully auditioned for the renowned Sixth Army Band.
How long did Phil Lesh stay with the Sixth Army Band?
Phil Lesh was ultimately determined to be unfit for military service.

Question: What did he major in at the College of San Mateo?
Self-contained rewrite: What did Phil Lesh major in at the College of San Mateo?