_Ut_—queant laxis. _Re_—sonare fibris. _Mi_—ra gestorum. _Fa_—muli tuorum. _Sol_—ve polluti. _La_—bia reati. Sancte Johannes. The fame of his wonderful results in choir-training, soon reached Rome, and the Pope, John XIX.,[264] sent an invitation to the still ostracized monk, to come to Rome. Guido is credited with having made many changes in the notation and harmony of his day. The hexachord system is attributed (justly or unjustly) to him. He also is said to have introduced lines of different colors into the staff, for the purpose of aiding the singer to recognize certain notes with more facility. He says in his _Micrologus_[265] “In order that sounds may be discerned with certainty, we mark some lines with various colors, so that the eye may immediately distinguish a note, in whatever place it may be. For the third of the scale [C] a bright saffron line. The sixth [F] adjacent to C is of bright vermilion, and the proximity of others to these colors, will be an index to the whole. If there were neither letter, nor colored lines to the Neumes, it would be like having a well without a rope—the water plentiful, but of no use to those who see it.” While Guido does not lay claim to having invented the colored lines, it is probable that he brought them, by his influence into much more general use. He certainly invented a modification of the line system of Hucbald. Instead of the inverted letters, and fragments of letters which the latter used, he employed the vowels only, to designate the pitch, thus,— ________________________________________________ ____________________________________tu-____|_u_| ______________so-______________________os__|_o_| F__ri-_____ri____lis________u-_____________|_i_| ________ve-_____________ter___ber-_________|_e_| Ma-___a______________Ma-__________a________|_a_| “Maria, veri solis mater, ubera tuos.” Guido, altered Hucbald’s _Organum_ in so far, that he rejected consecutive fifths, as being too harsh, and substituted a series of consecutive fourths as being milder.