Looks good. Just a couple minor things that popped out at me:
"In general, each fret is a half-step higher than the previous fret."
It's always a half-step. I'm sure you know that and it's just a nervous writing habit

If you're writing an article you want to sound as authoritative and sure of yourself as possible. Quite a few years back I got a great tip from a much better writer than me: Never write things like "I think," "If you ask me," "In my opinion," to start off your statements in an article! Rules are made to be broken of course, but it's generally a very good guideline. People that aren't used to writing articles will often put those kind of statements before something that is actually a fact! For example if you were to say something like, "In my opinion, you should establish a daily practice routine consisting of scales, arpeggios, sight reading, and rhythmic exercises." Wouldn't it be better if you get rid of that "In my opinion" statement? Of course it would be.
"Adjust your strap so that the bass falls at a comfortable level across your chest. In general, your bass should be at about the same level as your belly button."
Again minor, you may want to say what part of the bass should be at belly button level.
"The term "Fretting" refers to..."
Fretting? I would go with fingering. I would probably call the Fretting section "Your Left Hand" or "Left Hand Technique" or something like that instead. Consequently, I would call the Plucking section "Your Right Hand" or "Right Hand Technique". Especially since you are talking about both plucking and picking.
Beyond that I didn't make it too far... But don't take that in the wrong way! Your article would benefit greatly by being split up into separate pages. As it is it's all on one humongous page and that can get tedious to read. Your TOC already is split up into chapters, make each chapter a separate page with a link to the previous, next, and home page. It's a similar issue as not splitting up paragraphs, writing in all caps, not using any punctuation, etc.. Your words are the same, but the way you lay it out will make a big difference whether your target audience makes it all the way through your article or not.
Hope this is helpful

You could turn this into a real killer article with a few tweaks!