Accuracy of pitch judgment for three sets of 12 sine-wave tones was studied in three experiments. Tone sets differed only in the spacing of stimulus frequencies within the range 175 Hz-2093 Hz. The frequencies for Triad spacing were derived from the (well-tempered) tonic chord with root F3; for Keyboard Interval spacing, each frequency corresponded to a different musical note; for Arithmetic Interval spacing, frequencies were spaced at predetermined Arithmetic Intervals without specific concern for musical correspondence. Musical listeners showed most accurate judgment and most rapid learning of pitch for Triad spacing, and showed no difference between Keyboard Interval and Arithmetic Interval spacing. Comparison of two interstimulus durations, 3 sec and 8 sec, indicated at the slower rate of presentation a small but significant improvement in judgment of the lower six tones for both Triad and Keyboard Interval spacing, and an increased number of octave errors for the higher six tones for Triad spacing. Non-musical listeners showed no differences between sets or rates of presentation. Some characteristics of decision rules for musical pitch recognition are discussed. (Author).