Now this editing of the texts must have implied the editing of the music also. In the middle ages the choir played a more important part than they do to-day in the Roman Church. For now the Service is complete without their part, as the priest says the whole Service whether the choir is there or not. But formerly it was different; all listened or took part, including the celebrant, while the choir sang. The latter had a very definite share in the liturgical order, which was incomplete without them; in particular, the soloists had full scope for their talents in the chants between the Epistle and Gospel. In view of this intimate relation between the choir and the altar, a revision of the text must almost necessarily have implied a revision of the music. And this is probably the chief part of his musical reform; in the saying about him, ascribed to Pope Adrian II., "Ipse Patrum monumenta _sequens renovavit_ et auxit." What was the musical material on which he had to work, which he had to put into shape, and to which he added new pieces? It is probably substantially represented by the Ambrosian chant as we find it in the oldest MSS. It seems most likely that it is the musical counterpart of the primitive liturgy organized, as is supposed, about the epoch of Pope Damasus, of which the Ambrosian, Gallican, Mozarabic, and Celtic are so many variations, due to national characteristics. Documentary proof of this is but scanty, but a study of the Lessons used at Mass supports the theory as far as the text is concerned. It is further recorded that at Monte Cassino the Ambrosian chant was fused with the Gregorian by order of Pope Stephen IX. (1057-8). Here the Pre-Gregorian chant is simply called Ambrosian. ANTIPHON [Illustration: Antiphon, Gregorian and Ambrosian] Gregorian O Sa-pi-en-ti-a, quae ex o-re Al-tis-sim-i pro-di-is-ti at-tin-gens a fi-ne us-que ad fi-nem, for-ti-ter su-a-vi-ter-que dis-po-nens om-ni-a: ve-ni ad do-cen-dum nos vi-am pru-den-ti-ae. Ambrosian O Sa-pi-en-ti-a, quae ex o-re Al-tis-sim-i pro-ces-si-sti at-tin-gis a fi-ne us-que ad fi-nem, for-ti-ter su-a-vi-ter dis-po-nens que om-ni-a: ve-ni ad do-cen-dum nos vi-am sci-en-ti-ae. INTROIT [Illustration: Introit, Gregorian and Ambrosian] Gregorian Gau-de-a-mus om-nes in Do-mi-no, di-em fes-tum ce-le-bran-tes in ho-no-re A-ga-thae mar-ty-ris: de cu-jus pas-si-o-ne gau-dent an-ge-li, et col-lau-dant Fi-li-um De-i. Ambrosian Lae-te-mur om-nes in Do-mi-no, di-em fes-tum ce-le-bran-tes ob ho-no-rem A-ga-thae mar-ty-ris: de cu-jus tro-phae-o gau-dent an-ge-li, et col-lau-dant Fi-li-um De-i. GRADUAL