The Critical Nexus: Tone-System, Mode, and Notation in Early Medieval MusicThe Critical Nexus confronts an important and vexing enigma of early writings on music: why chant, which was understood to be divinely inspired, needed to be altered in order to work within the then operative modal system. To unravel this mystery, Charles Atkinson creates a broad framework that moves from Greek harmonic theory to the various stages in the transmission of Roman chant, citing numerous music treatises from the sixth to the twelfth