Harmony

See also what's at Wikipedia, your library, or elsewhere.

• Music theory

• Cours d'Harmonie Théorique et Pratique (4th edition, in French; Paris: L. Escudier, ca. 1857), by François Bazin (multiple formats at archive.org)
• Die Metalogik: Die Musikalische Logik, Geometrie der Empfindungen (in German; Munich: Musarion verlag, 1919), by Walter Harburger (page images at HathiTrust; US access only)
• Harmonielehre (4th revised edition, in German; Stuttgart: C. Grüninger, ca. 1915), by Rudolf Louis and Ludwig Thuille (page images at HathiTrust; US access only)
• Harmonielehre (7th edition, in German; Stuttgart: C. Grüninger, ca. 1920), by Rudolf Louis and Ludwig Thuille (multiple formats at archive.org)
• Leitfaden zum Praktischen Erlernen der Harmonie (German translation; Leipzig: P. Jurgenson, c1899), by Peter Ilich Tchaikovsky, trans. by Paul Juon
  • multiple formats at archive.org
  • page images at HathiTrust; US access only
• Manuel de l'Harmonie (translated into French from the 3rd German edition; Leipzig: Breitkopf and Härtel, 1902), by Hugo Riemann (page images at HathiTrust; US access only)
• Traité d'Harmonie, à l'Usage des Cours de l'École (in French; Paris: École de Musique Classique, 1889), by Gustave Lefèvre
  • multiple formats at Google; US access only
  • multiple formats at archive.org
  • page images at HathiTrust; US access only

Items below (if any) are from related and broader terms.

• Harmonielehre (4th revised edition, in German; Stuttgart: C. Grüninger, ca. 1915), by Rudolf Louis and Ludwig Thuille (page images at HathiTrust; US access only)
• Harmonielehre (7th edition, in German; Stuttgart: C. Grüninger, ca. 1920), by Rudolf Louis and Ludwig Thuille (multiple formats at archive.org)
• Understanding Basic Music Theory, by Catherine Schmidt-Jones (multiple formats at cnx.org)

• Harmonies of the World, by Johannes Kepler, trans. by Charles Glenn Wallis (HTML with commentary at sacred-texts.com)

• An Introduction to the Skill of Musick (London: John Playford, 1655), by John Playford (PDF at shipbrook.net)

• Gamut, by Music Theory Society of the Mid-Atlantic (full serial archives)

• Cours de Contre-Point Théorique et Pratique (in French; Paris: H. Le Moine, ca. 1881), by François Bazin (page images at HathiTrust)

• Sounding the Depths: Tradition and the Voices of History (2011), by Victor Grauer (HTML with commentary at blogspot.com)

• The Art-Work of the Future, by Richard Wagner, trans. by William Ashton Ellis (HTML at belgacom.net)
• The Birth of Tragedy Out of the Spirit of Music, by Friedrich Wilhelm Nietzsche, trans. by Ian C. Johnston
  • HTML in Canada
  • PDF with commentary at Richer Resources Publications
• Die Metalogik: Die Musikalische Logik, Geometrie der Empfindungen (in German; Munich: Musarion verlag, 1919), by Walter Harburger (page images at HathiTrust; US access only)
• The Magic of Tone and the Art of Music, by Dane Rudhyar (HTML at khaldea.com)
• Music and Meaning (Cambridge, MA: Harvard University Press, 1932), by Elizabeth Robinson Woods (page images at HathiTrust)
• Music Ho! A Study of Music in Decline (c1934), by Constant Lambert (HTML in Canada; NO US ACCESS)
• Opera and Drama, by Richard Wagner, trans. by William Ashton Ellis (HTML at belgacom.net)

• Sounding the Depths: Tradition and the Voices of History (2011), by Victor Grauer (HTML with commentary at blogspot.com)

• Music as Cultural Practice, 1800-1900 (Berkeley: University of California Press, 1990), by Lawrence Kramer (HTML at UC Press)

• The Rebirth of Hindu Music (online second edition), by Dane Rudhyar (HTML at khaldea.com)

• A Briefe Discourse of the True (But Neglected) Use of Charact'ring the Degrees, by Thomas Ravenscroft (HTML and page images at pbm.com)

• Learning to Read Music, by Peter Nickol (illustrated HTML with commentary at HowTo)

• A New Booke of Tabliture, Containing Sundrie Easie and Familiar Instructions (1596), by William Barley (PDF at shipbrook.net)