Posting because as a former piano kid who never really got music theory, the practice exercises and the embedded YouTube examples really helped me grok some stuff that was black magic to me previously.
This is really well done basic instruction. (I had to wait for college to get.)
PDF downloads
August 2020 edition (53 MB) - https://musictheory.pugetsound.edu/hw/MusicTheory-Aug-2020.p...
Homework assignments and practice tests - https://musictheory.pugetsound.edu/hw/MT21C-HOMEWORK-EXERCIS...
Practice exercises - https://musictheory.pugetsound.edu/hw/MT21C-PRACTICE-EXERCIS...