Did you know that Yale Library provides access to a number of Cambridge History of Music volumes from American Music to World Music. Here's a listing of all of them [1].

The Cambridge History of American Music
The Cambridge History of Eighteenth-Century Music
The Cambridge History of Musical Performance
The Cambridge History of Nineteenth-Century Music
The Cambridge History of Seventeenth-Century Music
The Cambridge History of Twentieth-Century Music
The Cambridge History of Western Music Theory
The Cambridge History of World Music