Very cool but what does this have to do with "21st-Century Classroom"? Is that just a meaningless phrase to make it sound modern, not old-fashioned?
I guess the 21st century classroom is the free online classroom you connect to from your portable device
It's a new presentation, an online hypertext, and uses YouTube publications of 21st Century music as example.
Could just be because it is the 21st century and this was written for classroom use.
If you subtract the "meaningless phrase", the title of the book is just "Music Theory". Do this for every book written about music, art, mathematics and you'll just have a lot of books with identical and quite dull titles.