Microchromaticism or microtonality

Some of the manuscripts from the city of Utrecht or its environment, Stavelot and Trier display special neumes that may indicate divergences from the 'normal' scale. This phenomenon is discussed in chapter VIII of Duitse en Nederlandse muzieknotaties ..., and in the introduction of the facsimile edition of NL-Uu 406 (pp. xvii-xix).

A similar phenomenon is encountered in the 11th century tonary Montpellier H 159, and in the Cluny gradual F-Pn lat 1087. For a comparison of these manuscripts see Ferreira: Music at Cluny.

For microtones see also D. Hughes in La musique et le rite sacré et profane (1986), vol. II, pp. 39 ff.