Abstract
This study examined performer, rater, occasion, and sequence as sources of variability in music performance assessment. Generalizability theory served as the study's basis. Performers were 8 high school wind instrumentalists who had recently performed a solo. The author audio-recorded performers playing excerpts from their solo three times, establishing an occasion variable. To establish a rater variable, 10 certified adjudicators were asked to rate the performances from 0 (poor) to 100 (excellent). Raters were randomly assigned to one of five performance sequences, thus nesting raters within a sequence variable. Two G (generalizability) studies established that occasion and sequence produced virtually no measurement error. Raters were a strong source of error. D (decision) studies established the one-rater, one-occasion scenario as unreliable. In scenarios using the generalizability coefficient as a criterion, 5 hypothetical raters were necessary to reach the .80 benchmark. Using the dependability index, 17 hypothetical raters were necessary to reach .80.