Hector Berlioz
Les soirées de l'orchestre (1852) (Link to 1895 fifth edition) English translation
Traité d'instrumentation (1855, second edition) English translation (excerpts)
A travers chants (1862)
Mémoires (1870)
See also this website devoted to Hector Berlioz, with many documents, images, and links.
Robert Schumann
Neue Zeitschrift für Musik (links to 19th century archives on Google books and other sites)
"Aus dem Leben eines Künstlers," Schumann's article on Berlioz's Symphonie fantastique, begins on p. 1 of the July 1835 issue, housed here along with a number of other issues. "Neue Bahnen," Schumann's 1853 article about Brahms, is on p185 of this issue. English translation of "New Paths."
Franz Liszt
Franz Liszt's Letters (1894 English translation on IMSLP; 1989 translation listed under Further Reading.) For a text-searchable version, see Project Gutenberg.
Felix Mendelssohn
Elijah, Op. 70
Complete text of the oratorio.
Video of "He, watching over Israel," from Elijah, performed in a magnificent setting by the famous Mormon Tabernacle Choir:
Das Jahr (1841)
Recordings on Spotify
Video of selections from Das Jahr played on a period instrument:
Links to WorldCat except where specified.
Berlioz, Hector. Evenings with the Orchestra, Jacques Barzun, trans. Chicago and London: University of Chicago Press, 1973.
Cairns, David. Berlioz, 2 vols. Berkeley and Los Angeles: University of California Press, 2000.
Cairns, David, ed. and trans. The Memoirs of Hector Berlioz. New York: Knopf, 2002.
Daverio, John. Robert Schumann: Herald of a “New Poetic Age.” Oxford and New York: Oxford University Press, 1997.
De Lara, Adelina. “Clara Schumann’s Teaching.” Music & Letters 26 (1945), 143–47. [link to JSTOR]
Gooley, Dana. The Virtuoso Liszt. Cambridge and New York: Cambridge University Press, 2004.
Hensel, Fanny Mendelssohn. The Letters of Fanny Hensel to Felix Mendelssohn, Marcia J. Citron, ed. and trans. New York: Pendragon, 1987.
Kimber, Marian Wilson. “The ‘Suppression’ of Fanny Mendelssohn: Rethinking Feminist Biography.” 19th-Century Music 26 (2002), 113–29. [link to JSTOR]
Liszt, Franz. An Artist’s Journey: Lettres d’un bachelier ès musique, 1835–1841,
Charles Suttoni, trans. Chicago and London: University of Chicago Press, 1989.
Macdonald, Hugh. Berlioz's Orchestration Treatise: A Translation and Commentary. Cambridge: Cambridge University Press, 2002.
Reich, Nancy B. Clara Schumann: The Artist and the Woman, rev. ed. Ithaca and London: Cornell University Press, 2001.
Rosen, Charles. The Romantic Generation. Cambridge, MA: Harvard University Press, 1995.
Schumann, Robert. On Music and Musicians, Konrad Wolff, trans.,ed. Paul Rosenfeld, trans. New York: Norton, 1969.
Todd, R. Larry. Fanny Hensel: The Other Mendelssohn. Oxford and New York: Oxford University Press, 2010.
Todd. R. Larry. Mendelssohn: A Life in Music. Oxford and New York: Oxford University Press, 2003.
Walker, Alan. Franz Liszt, 3 vols. Ithaca, NY: Cornell University Press, 1987–97.
Weissweiler, Eva, ed. The Complete Correspondence of Clara and Robert Schumann, 3 vols., Hildegard Fritsch and Ronald L. Crawford, trans. (New York: P. Lang, 1994-2003)