This definitive study takes as its subject a group of melodies copied many times, even within single manuscripts. Professor Randel is therefore able to base his conclusions about the relationship of the manuscript sources to one another on twenty-six separate Spanish manuscripts. He shows that there were actually four distinct traditions associated with these manuscripts instead of two as formerly assumed. By comparing the four traditions, he draws new conclusions about the relative antiquity of the written tradition for these psalm tones, the presence or absence of a modal system in the Mozarabic chant, and the development of the two general types of notation. Originally published in 1969. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.