Experimental design. Auditory stimuli consisted of sequences of five monaural tones of frequency Type A or B, presented in experimental blocks of Type X or Y, which were later collapsed together. In X blocks, standard sequences (74%) consisted of 4 repetitions of the same tone in one ear, followed by a fifth one in the opposite ear. These were interspersed with rare, unpredictable deviant sequences where the fifth tone was either different in frequency type (13%) or was omitted (13%). Y blocks were similar, except that the standard sequences had a fifth tone differing in frequency type. This effectively created an orthogonal contrast between temporally local versus global deviance in the pattern of tones. Omission sequences were unexpected in experimental blocks. These were contrasted with predictable repetitions of four-tone omission sequences in two additional control blocks.