Finite-state sequences were generated bya digital computer, converted to interval-coded pulse sequences, and transduced to sound by means of earphones. Within each block of B successive intervals, (B − 1) intervals were randomly selected and the Bth interval was selected to achieve a fixed parity sum over the block. Discriminability among the sequences—as measured by interstate interval thresholds-reflects both the specific form and the extent of the sequential restrictions introduced by parity. Parity restrictions upon interval-coded sequences may bediscriminable through modification of distributions of runs.