When presented with alternating low and high tones, listeners are more likely to perceive 2 separate streams of tones ("streaming") than a single coherent stream when the frequency separation ([delta]f) between tones is greater and the number of tone presentations is greater ("buildup"). However, the same large-[delta]f sequence reduces streaming for subsequent patterns presented after a gap of up to several seconds. Buildup occurs at a level of neural representation with sharp frequency tuning. The authors used adaptation to demonstrate that the contextual effect of prior [delta]f arose from a representation with broad frequency tuning, unlike buildup. Separate adaptation did not occur in a representation of [delta]f independent of frequency range, suggesting that any frequency-shift detectors undergoing adaptation are also frequency specific. A separate effect of prior perception was observed, dissociating stimulus-related (i.e., [delta]f) and perception-related (i.e., 1 stream vs. 2 streams) adaptation. Viewing a visual analogue to auditory streaming had no effect on subsequent perception of streaming, suggesting adaptation in auditory-specific brain circuits. These results, along with previous findings on buildup, suggest that processing in at least 3 levels of auditory neural representation underlies segregation and formation of auditory streams. (Contains 1 footnote, 2 tables, and 7 figures.)