Western Plainchant: A Handbook

David Hiley's handbook is the leading scholarly reference on Western plainchant, and its documented contribution here is specific: it traces Guido of Arezzo and the eleventh-century hymn Ut queant laxis as the actual historical source of the solmization syllables, the same syllables the modern Solfeggio frequency movement borrows its name from without the historical claims that movement makes. That direct textual and historical grounding, checkable against the sources Hiley cites, is the handbook's real evidentiary basis. This record has not independently traced further scholarly disagreement with Hiley's specific claims since 1993. Use it for the documented history of solmization and plainchant notation; it is not evidence for any modern claim about the Solfeggio frequencies' own effects, which needs a separate source addressing that specific modern claim.