Dh is quite proficient a few instruments, but has never really done any music theory.
He is now teaching the dc music, and although ds2 is quite musical like dh, ds1 isn't (he takes after me!). He is, however, quite mathsy, and so dh feels he would really love music theory as a key into music.
Problem is, he's not sure where to start, and so has been putting it off.
Could someone point me to some good books/resources he could look at for himself and/or use with the dc. Dh will put in the work required to get himself up to scratch so he can teach ds1, no problem, but it would be a shame to spend time and money on material which is not that great.
Any suggestions most gratefully received!