Try this website ... it is called the History of Classical Music.
I could not get to the website. I will try again because it sounds useful. In the mean time I have two ideas. Book: A History of Western Music by Donald Jay Grout, published by those careful folks at Norton. You might get a good cheap used copy at ABS.com Video: You might take a fancy to Lenny Bernstein's series from back in the late 50's and early 60's. It was done for "Young Persons", but it is charming and brilliant, as is Britten's remake of Purcell called "The Young Person's Guide to the Orchestra" which similarly is for all of us. Lenny was as much a teacher as a composer or conductor. You can get it used on VHS or now on DVD. To link the two suggestions, he went on to deliver the Norton lectures at Harvard which are on CBS or now DVD.