Provides information on the orchestral requirements, descriptions of each movement, and the historical background for concertos and symphonies by major composers.
This is more or less a collection of program notes written for the New York Philharmonic over a few decades, from what I understand, so it covers off *most* of the major orchestral repertoire plus throwing in a few obscure pieces that possibly got an outing during the author's time of writing notes.
You would need a bit of musical knowledge to keep up with Downes' notes, which contain musical examples and references to musical theory, but on the whole, they contain enough stories about each composition and what to listen for that it was an enjoyable book to work through (over many, many years) to listen to the repertoire.
The main drawback was that sadly the binding cracked and the book fell apart. So as a result, I was left with a stack of loose pages. As such, I decided to pretty much throw out a page as soon as I'd listened to the work and worked it down from 1000+ pages down to an empty paperback cover. I might one day go back and see if I can buy a second-hand hardback of this, because it is a great reference work. But for now, it guided me to a lot of classical works, and for that, I am glad.