Musically significant, automatic localisation of note boundaries for the performance analysis of vocal music
Nicholas J. Bailey, Douglas McGilvray, Graham Hair · 2008
Hair’s recent compositions for voice include works composed in the 19-ET system. One of the primary motivations for the move away from 12-ET is a more extensive chromatic variety [11]. Works such as Ash require a significant effort to “retune the ear” of conservatory-trained musicians: they have spent most, if not all, of their careers performing in standard 12-ET tuning or at least in tuning systems which explicitly admit only twelve divisions of the octave. Having delivering advanced, 19-ET capable ear-training software, there is a motivation better to understand the emergent performance structures, essentially the performance tradition, of such music. Previous published work on automatic transcription determines note onset simply by awaiting a temporarily stable pitch, or removes the effect of vibrato by averaging the pitch trajectory over time. A detailed measurement of the pitch trajectories of expert performers, and separately, of each note’s inflections needs to be made, so that this information can be interpreted in the context of composed harmonic and melodic structures. We describe two specially developed segmentation algorithms in application to vocal music. In both cases, particular attributes of the music would make it likey that naive algorithms would fail. Firstly, pitch-based segmentation is undertaken in a piece where the smallest chromatic interval is 1/19th of an octave. This presents the algorithm with pitch resolution problems more stringent than pitch-based segmentation in 12ET. The algorithm has been deployed as a rehearsal aid for repertoire-specific training of expert musicians at the Royal College of Music[5]. The second example demonstrates the use of vector quantisation to establish significant pitch-trajectory characteristics in a recording of Schoenberg’s Pierrot Lunaire. The source material was recorded especially by the soprano Jane Manning, an internationally recognised authority on the performance of this piece whose first recording of it dates from 1967[9].