This article examines conditions under which tones standing in octave relation are treated as equivalent by the perceptual system. According to the two-channel model for the abstraction of pitch relationships proposed by Deutsch (1969, 1982), octave equivalence effects should not operate directly in the processing of melodic intervals. In an experiment to test this prediction, it was found that accuracy in immediate recall of pitch sequences was substantially lower when the tones within a sequence were distributed across two adjacent octaves than when they were all in the same octave. This finding is in accordance with the two-channel model. Its implications for musical processing, together with those of other studies on octave equivalence, are discussed.