Octave discrimination: temporal and contextual effects

Abstract

Discrimination of the musical octave was studied using the psychophysical method of constant stimuli. Stimuli were two successive pure tones whose ratio varied in discrete steps from 100 cents below to 100 cents above the physical octave of 1200 cents. Listeners judged whether each pair was flat or sharp with respect to a correctly tuned octave. Two measures were estimated for each of ten listeners. The first was a measure of sensitivity, the difference limen. The second was the subjective criterion for the octave, or that tuning judged equally likely to be sharp or flat. For two tones in immediate succession the results were in accord with previous investigations: the discrepancy between the subjective octave and the physical octave was typically in favour of a `stretched' subjective octave about 20 cents wider than the physical octave. However, the magnitude of the stretch decreased, and sensitivity of discrimination increased, when the two tones were separated either by silence or by two musically related tones-in this case, the notes of the equal-tempered major triad. The results suggest that the criterion for the subjective octave is influenced by context and by the listener's strategy. Thus, in music, a flexible choice of tuning criteria may be desirable