"Barbara Allen": Tonal versus Melodic Structure, Part II

Abstract

ronson's classification of tonal structures, used in his monumental work The Traditional Tunes of the Child Ballads, represents a consistent application of the principle of gapped scales. He demonstrates his system by means of a diagram termed mode-star (Bronson 1962:xi-xiii). Each of the seven star-points signifies a heptatonic mode. Although the Ionian (or major) is placed on top, the chain actually does not start with the Ionian but with the Lydian mode (contrary to the opinion expressed by Bronson). Proceeding clockwise one arrives at the following series: Lydian (Ly), Ionian (I), Mixolydian (M), Dorian (D), Aeolian (Ae), Phrygian (P), and Locrian (Lo). To show the coherence of this arrangement Bronson stresses the fact that the tone material of each succeeding mode corresponds to that of the plagal form of the preceding one. For example, cdeFgabc (plagal Lydian) has the same tone material as Cdefgabc (authentic Ionian); gabCdefg (plagal Ionian) has the same tone material as Gabcdefg (authentic Mixolydian), and so forth. When a common tonic is chosen, adjacent modes are identical except for one degree: Ly=I save the 4th degree; I=M save the 7th degree, and so forth. Consequently, a hexatonic scale which lacks such a distinctive degree is neutral in its allegiance (as scale) to the heptatonics on either side (ibid.). For example, the scale Cdegabc belongs between the Lydian and the Ionian mode because the lacking 4th degree can be either F# or F; therefore, the scale is to be classified as LydianIonian (Ly/I); similarly, the scale Cdefgac is Ionian-Mixolydian (I/M), and so forth. Pentatonic scales are equated to heptatonic ones lacking two degrees. For example, the scale Cdegac lacks the 4th and 7th degree; therefore, it