This study sought to determine if an objective measurement of instrumental music achievement could be obtained on sight-reading rhythms and if it could differentiate degrees of attainment. Through the utilization of concepts introduced by Joseph Schillinger, mathematical constructs were used to develop equivalent forms of an individual instrumental music performance test. Complete test protocols for 771 subjects at the 5th grade level or above revealed a high degree of consistency for the two forms of the test. Randomly selected tape recordings of testing sessions reflected a high degree of scorer reliability. Multiple and partial correlations revealed the importance of experience to performance, and t-test results indicated differences between any two levels of experience when experience was defined in years.