THE NOTATION OF DYNAMIC LEVELS IN THE PERFORMANCE OF ELECTRONIC MUSIC

The “sound diffusion” (or “sound projection”), that is, “the projection and the spreading of sound in an acoustic space for a group of listeners”[1], of works for solo electronics or for acoustic instruments and electronics (so called, “mixed pieces”), has always raised the issue of notating the levels to be reproduced during a concert or the correct balance between the electronics and the instruments. If, in the last decades, some attempts were made by few composers or computer-music designers, mostly in the form of scores, none of these managed to establish a common practice. In addition, little theoretical work has been done so far to address the performative aspects of a piece, that is, to provide just the useful information to the person in charge of the sound diffusion. Through the discussion of three historical examples and the analysis of two experiences we developed, we will try to identify some possibly general solutions that could be adopted independently on the aesthetic or technological choices of a given piece. 1. PRELIMINARY CONSIDERATIONS The notation of electronic music has generated only few, often partial, essays. Most of the literature is either quite theoretical [2], or it delves into the automated translation of electronic sounds into a sort of graphical score, such as in [3]. These experiments were mainly aimed at providing ways to analyse purely electronic pieces more deeply than when simply listening to them, to account for the compositional process, or as an attempt to digitally preserve and archive cultural assets [4]. To our knowledge, little theoretical work has been done to tackle the more general issue of how to notate dynamic levels on a score that is to be read by the computer music performer (CMP) who will perform the electronics during a concert. The CMP does not need to be the composer or the first performer of the piece. Although this task could be programmed on a computer and automated during the concert, a much better result can be achieved when doing it by ear. The listening and musical skills of a human being are, in fact, still much superior to what a machine can realize. The sound diffusion can be adapted to the acoustics of the hall, the properties of the loudspeakers, the whole audio system, the relationship between these and the acoustic image of the instruments on stage, whether they are amplified or not, and, finally, to the emotional reaction of the audience. As a consequence, most of the time, the dynamic levels are controlled by ear (and by hand) by the CMP or the composer. Often they are only roughly sketched on the score. If a faithful recording will certainly help as a reference, the information is usually insufficient, especially in the case of particular spatial configurations that cannot be reproduced by a stereo recording. Therefore, the most effective solution is to notate all the information about the sound diffusion directly on the score that will be used during the performance. To delimit our scope, we will concentrate on the notation of dynamic levels and will not tackle the issue of notating other parameters used for real-time sound processing, such as, for instance, the transposition factor of a harmonizer. 1.1 Levels vs. loudness vs. musical dynamics Objectively, levels are normally expressed in decibels, a logarithmic unit that is related to the ratio between the value of a given and of a reference sound pressure (usually, either the threshold of audibility, or the maximum available value in a given system) 1 . However, there are other ways to do it: from the point of view of the perception, the dynamic levels are called “loudness” and use phons (a unit that takes into account 1 See http://en.wikipedia.org/wiki/Decibel (accessed 3/10/2015) Copyright: © 2015 Carlo Laurenzi et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License 3.0 Unported, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. the psycho-acoustic effect of the equal-loudness curves ISO 226:2003) 2 ; from a musical point of view, levels are called “dynamics” and use symbols such as ff, mf, pp. Three important factors need to be taken into account: first, the same musical dynamics played by different instruments, or in different ranges of the same instrument, might yield different objective or perceptual levels; second, choices of interpretation play an important role and produce different absolute levels for the same musical dynamics, as pointed out in [5] 3 ; third, the perception of an acoustic instrument’s crescendo is always associated to the production of a richer and broader spectrum, that is, to a shift of the spectral “centre of gravity” toward a higher value. These spectral aspects differ specifically from each instrument and can be easily demonstrated by recording three sound files at three different dynamics (say, pp, mf, ff), clean them from background noises and finally normalize them. Even though they have the same maximum amplitude, their dynamics can be easily and correctly identified. Hence, simply raising a fader will not be sufficient to convey a real feeling of crescendo, but rather of a sound getting closer. When notating levels into a performance score, which unit should be used: dBs, loudness or musical dynamics?