For Music Theory
Link to free blank staff paper
The Language and Materials of Music Third Edition
by Kendall Durelle Briggs
Link: http://a.co/5rU0jzY
For a deep-dive into Common Practice music theory, this book is for you!
Mark Sarnecki Music Theory, Second Edition
by Mark Sarnecki et al.
Link: http://a.co/1hehpBV
Comprehensive coverage in three levels for late-elementary or early-intermediate students.