He was the author of five books, including Source Readings in Music History, Music in Early Christian Literature, and The Advent Project: The Later Seventh-Century Creation of the Roman Mass Proper, which attempts to reconstruct the history of plainchant from the Patristics (Early Church Fathers) to the Carolingian period. He also edited the collection The Music of Antiquity and the Middle Ages which includes chapters he wrote on early Western civilization, Christian antiquity and the emergence of Gregorian chant. McKinnon published more than one hundred articles in music journals and reference books.