The Role of Acoustic Signal Partitions in Listener Categorization of Musical Phrases

Abstract

An experiment was designed to assess the relative contribution to listener categorization strategies of various temporal partitions of the acoustic signal for trumpet, clarinet, and violin. The role of context, whole phrase versus single note, was also evaluated. Analog recordings of three folk-song phrases performed on two clarinets, violins, and trumpets were digitized. A computer program was developed for digital signal editing. Signal edit conditions included normal, time-variant steady-state alone, transients alone, and static steady state with and without transients. Musicians and nonmusicians responded to a matching procedure in which unedited signals of one phrase were choice stimuli and edited signals for two different phrases served as models. Two replications of all possible combinations of instrument, phrase, and edit conditions were presented for a total of 72 items. Two additional groups of musicians and nonmusicians participated in an identical procedure in which the stimuli were single notes extracted from two phrases. Analyses revealed that, for the whole-phrase signals, there was no case in which the means obtained with the "normal" signal and the "time variant steady state alone" signal were statistically different; these means were always statistically higher than the "transients alone" mean. It was concluded that transients were neither sufficient nor necessary for the categorization of trumpet, clarinet, and violin in whole-phrase contexts. The time- variant quasi-steady state was sufficient and necessary for the categorization of trumpet and violin phrases, and it was sufficient but not necessary for the categorization of clarinet phrases. For the single- note stimuli, "transients alone" yielded means statistically equivalent to the "normal" and "time variant steady state alone" means. It was concluded that transients were sufficient, but not necessary, for instrument categorization in single-note contexts. The whole-phrase context yielded significantly higher means than the single-note context; music majors performed the task with greater accuracy than nonmusic majors.