I use working memory reason for DD to practice. The gross motor skills, the fine motor skills and the reading of the music combined make for working memory increases. (went to the lecture) And why only piano and strings have the increases. Not brass, or drums or vocal lessons. They tried acting lessons too in the study, which improved confidence but nothing for IQ.
I wouldn't be able to answer for brass, but:
- Vocal music requires very little understanding of music. You don't have to understand keys, chords, or scales, since these things pretty much take care of themselves by ear. The actual notes, intervals, and rhythms can also be learned entirely by ear and repetition, with sheet music providing some relative hints. You don't need to know that an interval is a third or a fifth, though... the sheet music can be just a guide, like "up a little here" or "up more here."
- Drums are more a physical activity than a mental one.
