The control of acoustic intensity during jazz and free improvisation performance
Roger Thornton Dean, Freya Bailes · Critical Studies in Improvisation / Études critiques en improvisation · 2010
The paper demonstrates the predominance of a pattern of acoustic intensity change in recorded improvisations in which intensity rises are shorter than falls and in which the rate of intensity change is greater in the rises than in the falls. A wide range of Western improvised music is studied, and the analyses are conducted by measuring intensity in moving windows across each piece. The windows used are 0.04 sec, 0.5 sec, 5 sec and 10 sec, chosen to sample a range of important musical structures such as patterns, phrases and phrase groups. In addition, a comparative analysis using detected rhythmic beats as the window, with slightly variable lengths, is presented. The recurrent pattern is interpreted in terms of a hypothesised Force-Effort-Energy-Loudness-Affect chain, linking performer (or composer) with listeners and with other performers. Partial experimental investigation of this chain in other work has been consistent with the theory in supporting a major role of acoustic intensity in the perception of both musical change and affect. It seems that improvisers share this patterning of acoustic intensity with interpreters of classical music, and composers of electroacoustic music. Thus we suggest that music made without acoustic instruments, that is without the physical intervention of performers providing the energy to activate a sounding instrument, has developed the same pattern because composers recognise its expressive power as a statistical archetype. It remains to be seen whether this statistical feature could have been assimilated from environmental and/or speech sounds.