Literature about piano, organ and harpsichord
ML410 - Composer biography, performance, criticism
ML 700 - Piano History and Criticism
Theory, How-to, Analysis, Performance
MT140 - Piano Music Analysis and Interpretation
MT145 - Analysis and Interpretation (composer specific)
M6-15 - Organ
M22-29 - Keyboard (Piano, harpsichord)
Go to Advanced Search and type the last name of the composer in one field and the op. and no. (in quotes) or thematic catalog number in the second field. Ex. Beethoven and "Op. 10 no. 2" Make sure you limit the format to "Music Scores".