Useful Subject Headings in the library catalog Searches.

In the library Catalog:

1. Choose Tab "Books & More"

2. Under the search box, click "Classic Catalog"

3. In the pull-down menu to the left of the search box, fill in one of the subjects below:

music theory

theory of music
chants (plain, Gregorian, etc.) - Instruction and study
chromatic alteration (music)
counterpoint
harmony
instrumentation and orchestration
music - philosophy and aesthetics
musical analysis
musical intervals and scales
musical meter and rhythm

Classicism in music
Composition
Counterpoint
Ear training
Embellishments (Music)
Music -- 17th century -- History and criticism
Music -- 18th century -- History and criticism
Music -- 19th century -- History and criticism
Music -- Textbooks
Music -- Instruction and study
Music theory -- Dictionaries
Music theory -- Elementary works -- Studies and exercises
Music theory -- Elementary works -- Study and teaching
Music theory -- Periodicals
Music theory -- Instruction and study
Music theory -- History
Musical analysis
Musical dictation
Musical form
Romanticism in music
Schenkerian analysis
Sight-reading (Music)
Tonality

A number of libraries around the world are digitizing primary souces materials from their collections. If you learn that a particular library holds a specific manuscript or edition, go to that library's website to disceern whether a digitizing version of it is available. Below are a few major research libraries: