My son (12 y.o.) would like to learn some basic lesson in music theory that will help him complement his intonation, phrasing, etc. He learns very basic music theory from violin teacher and a pianist who would accompany him for recitals etc. He knows basic intervals like 3rd, 6th, octaves, etc. from playing the scales, but say.. if he play a certain passage from a piece, he wouldn't necessarily knows what is the harmony of the passage (is it minor? major? what is the chord?). As I understand it, it will help with phrasing, understanding which part of the score is tension v.s. resolution, etc. (yes, he needs to learn basic musical terms as well beyond dynamic markings, etc.)
We welcome suggestions either online programs, books, self-study, apps, videos/YouTube, summer camps (??) etc. so long as it can be applied to his violin playing. Any advice would be appreciated. Many thanks in advance!