The effects of deviation and phase disparity of frequency and amplitude modulation on musical blend

Abstract

Two experiments tested the effects of deviation and phase disparity of frequency and amplitude modulation on an aspect of musical blend referred to as fusion. The experimental procedure was a two-alternative forced choice design. The stimuli were two simultaneously presented complex tones in a musical interval of a major sixth. The spectral envelopes of the complex tones were similar to oboe tones at fundamental frequencies of 312 and 523 Hz. These tones were modulated by a sinusoid at a rate of 5 Hz. Frequency and amplitude deviations representative of musical instrument vibratos were constructed with peak frequency deviation varying by 0% (unmodulated), 1.0%, and 2.2%. Amplitude modulation indices were subjectively matched to the tone quality of the frequency modulation deviations. Also, the modulation of one tone relative to the other tone in a stimulus was varied by 0, 45, 90, and 180 deg. Both tones of a stimulus had the same deviation but they could differ in phase of modulators. Results show subjects were attuned to deviation where greater deviations decreased the amount of fusion. However, subject variability showed two other decision strategies occurring; a combination of deviation and phase disparity, and phase disparity alone.