Charlemagne was particularly interested in St. Gall but was also concerned with the monastic centers at Mainz, Fulda, Treves, Cologne, Bamberg, Hersfeld, Lorsch, Würzburg and Reichenau.[24] He founded Neustadt and endowed twelve monasteries in Germany. Meanwhile missionary zeal had guided Benedictine pioneers beyond the old boundaries, and Bavaria and Frisia had already been opened to missions and incidentally to the full round of Benedictine activities. Louis the Pious was active in monastic reform through his association with Benedict of Aniane; he was a special patron of St. Gall and he stimulated the efforts of leaders from Corbie to found New Corbie. Charles the Bald was a benefactor of Marchiennes, Compiègne, Prum and St. Denis.[25] Prior to this period, the numerous and influential foundations established on the continent by Irish monks had adopted the Benedictine Rule, swelling the total number of centers devoted to religious and educational activities. The numerical increase in the Benedictine abbeys offers in itself presumptive evidence of a greater use of hymns. What is known of the monastic centers and their store of hymnaries offers direct proof. A closer bond between the Order and the cultural activities of the age is found in the great personalities drawn from Benedictine ranks to serve the imperial designs. Of particular interest here are the statements regarding hymns and hymn singing which appear in contemporary writings. Alcuin was chiefly interested in the Roman liturgy as such but he wrote _De psalmorum usu_, _Officia per ferias_ and the _Epistolae_, the last of which shows a special interest in music. Rabanus Maurus testifies to the general use of hymns by secular as well as regular clergy. Amalarius of Metz mentions the use of hymns outside the monasteries. Walafrid Strabo traces the use of hymns from the time of Ambrose and repeats the Canon of Toledo recommending hymns. He says that churches which do not use hymns are exceptional.[26] The testimony is scattered but it points to the adoption of the hymnal by the secular clergy. It should also be recalled that the Ambrosian tradition of musical independence was constantly maintained at Milan. As the Latin language became more and more an exclusive clerical possession, the old safeguards provided by monastic walls were no longer necessary. The whole body of clergy whether regular or secular became the custodians of the hymnaries used in monastic and diocesan centers of music and scholarship.[27] The Christian laity of Europe at this period may have been largely ignorant of their hymnic heritage because the Carolingian extension of hymn writing and hymn singing occurred within clerical ranks. There was at this time scant indication of the future course of Latin hymnology which would ultimately restore to the layman his original possession handed down from the Early Christian Church.