Where's My Textbook for the Course?
Now a word about potential downsides to this approach. The quality of online materials differ. Traditional textbooks published by reputable companies go through a rigorous adjudication process to ensure quality and accuracy. This kind of rigor does not get applied to most OER. Yes, I do evaluate all the materials ahead of time before you see them. I have a pretty good handle on all that, but I am not an authority in every aspect of music. Also note, that as a last resort--when I cannot find suitable online articles to cover a particular topic--I resort to Wikipedia, which as you know as its strengths and drawbacks as well.
Advertising in Education: Don't Get Me Started
I hate even having to address this topic, but it keeps coming up. Without a traditional text and having to rely on OER, some sites will promote advertising, especially when I link you to You Tube videos, which is the best source for many musical examples. My personal opinion is that in our consumerist society we have way too much advertising that bombards us, plays with our minds, and instructs us to buy, buy, and buy some more. That gets you to buy stuff, which is supposed to increase manufacturing (but the USA does not manufacturer much anymore), and keeps the economy going. So that is the rub of the grain, and it is a big tradeoff. Be patient with the advertising for now. Hopefully, the direction of online education will steer away from this in the future. For now, we have to put up with some of it. I have tried to keep it to a minimum.