A biography of Louis Abbiate, truly an unsung hero of cello and piano music. Peter Dzialo has recorded many of his solo cello works, including the Préludes et Fugues, 13 Prélude-Etudes, and the Grand Symphonic Etude.
Morton Latham's biography of famous cellist Alfredo Piatti. LPR has recorded Piatti's complete Caprices for solo cello. Purchase that recording here.
De Musica. The first two sections of Book 1 from the De Musica of Boethius (6th century A.D.). He discusses the power and importance of music in forming character and the three kinds of music: cosmic, which pertains to the order found in the things of the cosmos; human, which pertains to the unity (consonance) found in man's body and soul; and instrumental, which pertains to audible sounds created by various instrumental means.
ION. Plato's dialogue between Ion, the reciter of poetry, and Socrates on the nature of poetic interpretation and inspiration. This is relevant to performing musicians since they stand as a middle between composer and audience in a way similar to how Ion stands between poet and audience.
Writings of Jacques Maritain on art.
Poetic Argumentation. An excerpt from John A. Oesterle's elementary logic text, Logic: the Art of Defining and Reasoning. This reading briefly outlines the relationship between poetry and logic, how the poet uses words and sounds, the role of the image in poetry, the sense in which poetry as art is moral, and its ends. These considerations are imperfectly applicable to music.
Address to Artists by Pope Benedict XVI.
Letter to Artists by Pope John Paul II.