When the phrase was formally sung, the Gregorian tones proper to it in the church service were employed. Some of these were florid successions of notes, many to a syllable, as in the Alleluia from which the Sequences sprung,—a free, impassioned form of emotional utterance which had extensive use in the service of the earlier Church, both East and West, and which is still employed, sometimes to extravagant length, in the Orient. The custom at last arose of setting words to these exuberant strains. This usage took two forms, giving rise in the ritual service to the “farced Kyries” or Tropes, and in the freer song of the people producing a more regular kind of hymn, in which the _Kyrie eleison_ became at last a mere refrain at the end of each stanza. These songs came to be called _Kirleisen_, or _Leisen_, and sometimes _Leiche_, and they exhibit the German congregational hymn in its first estate.
Religious songs multiplied in the centuries following the tenth almost by geometrical progression. The tide reached a high mark in the twelfth and thirteenth centuries under that extraordinary intellectual awakening which distinguished the epoch of the Crusades, the Stauffen emperors, the Minnesingers, and the court epic poets. Under the stimulus of the ideals of chivalric honor and knightly devotion to woman, the adoration of the Virgin Mother, long cherished in the bosom of the Church, burst forth in a multitude of ecstatic lyrics in her praise. Poetic and musical inspiration was communicated by the courtly poets to the clergy and common people, and the love of singing at religious observances grew apace. Certain heretics, who made much stir in this period, also wrote hymns and put them into the mouths of the populace, thus following the early example of the Arians and the disciples of Bardasanes. To resist this perversion of the divine art, orthodox songs were composed, and, as in the Reformation days, schismatics and Romanists vied with each other in wielding this powerful proselyting agent.
Mystics of the fourteenth century—Eckart, Tauler, and others—wrote hymns of a new tone, an inward spiritual quality, less objective, more individual, voicing a yearning for an immediate union of the soul with God, and the joy of personal love to the Redeemer. Poetry of this nature especially appealed to the religious sisters, and from many a convent came echoes of these chastened raptures, in which are heard accents of longing for the comforting presence of the Heavenly Bridegroom.