As a measure of musical aptitude, a new 90-item Pitch Discrimination Test was developed, and its internal structure was examined. Each of the three sections of the test measures an individual's aptitude for pitch discrimination in a different frequency range using square-wave tones generated by a personal computer. A total of 1,303 examinees, mostly clients taking aptitude tests for career guidance, completed the new worksample 740 A and the current version 315 F. The analyses reported were conducted with a minimum of 1,270 examinees; the exact number of cases for any given analysis varied slightly as a function of missing values on some variables. Representation of both sexes was nearly equal, and the median age of examinees was 26 years. The internal structure of Worksample 740 A was assessed using several methods: (1) comparisons with Worksample 315 F; (2) reliability analysis; (3) factor analysis; (4) item fit analysis; and (5) item difficulty analysis. Obtained reliability coefficients for Worksample 740 A were higher than those of Worksample 315 F. With a few exceptions, all items contributed to the test's reliability. Factor analysis indicated that all sections measured the same underlying construct. Analysis of age and sex indicated that age, but not sex, requires careful consideration in construction of norms for the new test. The new instrument allows the Johnson O'Connor Research Foundation to provide examinees with a more generalizable assessment of their aptitudes for pitch discrimination. (SLD)