The Codex Calixtinus is a 12th century illuminated manuscript formerly attributed to Pope Callixtus II, though now believed to have been arranged by the French scholar Aymeric Picaud. It was intended as an anthology of background detail and advice for pilgrims following the Way of St. James to the shrine of the apostle Saint James the Great in Galicia. The collection includes sermons, reports of miracles and liturgical texts. The Codex Calixtinus was intended to be chanted aloud and is of great interest to musicologists as an early example of polyphony. In particular, it contains the first known composition for three voices, the conductus Congaudeant catholici (Let all Catholics rejoice together); however, the extreme dissonance encountered when performing all three voices together has led some scholars to suggest that this was not the original intention. The popularity of the music has continued to the present day with modern recordings commercially available.