The Sound of Medieval Song is a study of how sacred and secular music was actually sung during the Middle Ages. The source of the information is the actual notation in the early manuscripts as well as statements found in approximately 50 theoretical treatises written between the years 600-1500. The writings describe various singing practices and both desirable and undesirable vocal techniques, providing a fairly accurate picture of how singers approached the music of the period. Detailed descriptions of the types and uses of improvised ornament indicate that in performance the music was highly ornate, and included trill, gliss, reverberation, pulsation, pitch inflection, non-diatonic tones, and cadenza-like passages of various lengths. The treatises also provide evidence of stylistic differences in various geographical locations.

McGee draws conclusions about the kind of vocal production and techniques necessary in order to reproduce the music as it was performed during the Middle Ages, aligning the practices much more closely with those of the Middle East than has ever been previously acknowledged.