A model based approach to automatic harmonization of a melody

Abstract

HarmTrace has shown to be an effective model to derive harmonic functions of chords in their tonal context. This article describes the addition of a chord generation and selection mechanism that investigates the abilities of the HarmTrace model as an automatic harmonizer that generates chords with a given melody. A system which is able to generate multiple harmonically well-formed chord sequences for a given melody is added to the model. From the generated sequences the best one is chosen, by means of smallest amount of parser errors. One experiment is carried out in which chord sequences for carefully selected melodies are generated. Subsequently, in a survey a panel of harmony experts are asked, based on listening to the model generated sequences, to describe their professional opinion and rating of these chord sequences. A second experiment is carried out in which a chord sequence for an selected melody is generated, and compared to the original accompaniment of that melody that is considered a ground truth. Unlike all currently existing systems, this system guarantees the generation of well-formed chord sequences, in which the constituents are automatically functionally explained with regard to their context. From the experiments, it is shown that the system is capable of generating correct chords per melody tone. However, it is also shown that harmonizing a melody with individually well-formed chord sequences from the HarmTrace grammar do not guarantee a harmonically well-sounding coherence between the sequence and the melody. This can be explained by the nature of the system, which built to analyze, rather than to create music.