Music Mindfulness - Introductory - Overview

The Listening Book (Mathieu)
The Musical Experience (Ratner)
Learning to Read Music (Lilienfeld)

48 Jewels - Well-Tempered Clavier and Bach

Bachanalia: The Essential Listener's Guide to Bach's Well-Tempered Clavier (Altschuler)
J. S. Bach's Well-Tempered Clavier: In Depth Analysis and Interpretation (Bruhn)
Counterpoint, Fourth Edition (Kennan)

Four-Chambered Heart - String Quartet - String Chamber Music

The String Quartet: a History (Griffiths)
The Great Haydn Quartets (Keller)
Joseph Haydn and the String Quartet (Barrett-Ayres)
The Beethoven Quartets (Kerman)
The Beethoven Quartet Companion
The Art of Quartet Playing
Guide to Chamber Music (Berger)
Chamber Music (Penguin)

Four-Chambered Heart - The Classical Period

Classic Music: Expression, Form, and Style (Ratner)
The Classical Style (Rosen)

General Music Reference

Harvard Dictionary of Music