books.google.com - This volume presents reprints of the prefaces to representative collections of metrical psalms. Psalm-singing, an essentially popular form of music, required some musical knowledge in the singers, and it was in these prefaces that the compilers gave basic information on the staves, clefs and note-values...https://books.google.com/books/about/English_psalmody_prefaces.html?id=HlAJAQAAMAAJ&utm_source=gb-gplus-shareEnglish psalmody prefaces
