How do we know what notes a composer intended in a given piece? -- how those notes should be played and sung? -- the nature of musical life in Bach's Leipzig, Schubert's Vienna? -- how music related to literature and other arts and social currents in different times and places? -- what attitudes musicians and music lovers had toward the music that they heard and made? We know all this from musical manuscripts and prints, opera libretti, composers' letters, reviews in newspapers and magazines, archival data, contemporary pedagogical writings, essays on aesthetics, and much else. Some of these...