With some justification musicologists have virtually ignored the group of writings by the Parisian chancellor Jean Gerson (1363–1429) entitled De canticis. The title notwithstanding, these three treatises, written between 1423 and 1426, provide much more commentary on the affects of the soul than on the effects of the vocal cords. Gerson, a reform-minded mystical theologian active at the Council of Constance, had no intention of becoming a music theorist; at times in these treatises he explicitly precludes any explanation of technical musical terms. Though many such terms are used, the reader is presumed to understand their literal meaning. It is the allegorical meaning that Gerson purports to explicate. Indeed the allegorical level is the most appropriate one for treating musical instruments, for the organ is virtually the only instrument from biblical times that was still used in late-medieval churches. Yet by the fifteenth century the treatment of instruments as symbols of states of the soul had long been commonplace, and Gerson fails to arouse new interest. Even less attractive to the modern reader is the spiritualisation of Guido's hexachord. By deleting one of the As (by changing fa to mi in mutation from soft to hard hexachords), the six syllables ut, re, mi, fa, sol, la can be reduced to the five vowels A, E, I, O, U, which in turn signify the five primary affections or emotions: joy, hope, compassion, fear, sorrow.