Various 1-, 2-, and 3-tone stimuli were presented to subjects, who had to judge how many tones were present. Discrimination of number of different tones sounding was far from perfect, even though Ohm''s acoustic law would lead us to expect high accuracy; discrimination did not improve even when frequency components were widely spaced. Accuracy of perception was poorer for 2- and 3-tone combinations than for 1-tone stimuli. Number of allowable response categories also affected the level of correct responses''. Individual differences in performance were large.