Abstract This article investigates the retention, reformation, and revision of plainchant in liturgical books printed in German-speaking lands during the early Reformation. Previous scholarship often considered chant in confessional and linguistic isolation, which has obscured both its importance in Protestant worship and its connections with contemporary Catholic musical trends. Writings of reformers and their followers, including Luther, Müntzer, and Spangenberg, indicate that they valued plainchant because it provided continuity, functioned pedagogically, and increased congregational unity. However, chant was subject to modification. An examination of reformed sources connected to Allstedt, Erfurt, and Nordhausen demonstrates how plainchant was adopted and adapted to reflect shifting priorities. Analyses of modified alleluia chants in Protestant and Catholic books reveal similarities and differences in techniques of revision. The formation of new musical traditions is delineated, as well as their intertwined relationships with the musical past, present, and future. These interconfessional findings provide new perspectives on early modern chant and liturgies.