1. Herman von Helmholtz, Die Lehre von den Tonempfindungen (1862). Translated as On Sensations of Tone, by Alexander J. Ellis from the 4th German edition (1877). Reprinted by Dover, New York, NY, 1954, p. 1.
2. John Tyndall, On Sound, D. Appleton, New York, NY, 1867. Third edition, reprinted under the title, The Science of Sound, Citadel Press, New York, NY, 1964. Preface to the First Edition.
3. Herman von Helmholtz, Die Lehre von den Tonempfindungen. This volume includes extensive commentary by Alexander Ellis, as well as an appendix by him on musical pitch.
4. John Tyndall, On Sound.
5. J.W. Strutt, 3rd Baron Rayleigh, The Theory of Sound, 1877. American reprinting of the second edition (1894), Dover, New York, NY, 1945.