Tekman, H. G. (2002).  Perceptual integration of timing and intensity variations in perception of musical accents.  Journal of General Psychology, 129, 181-191.

Detection of timing and intensity variations in tone sequences was investigated within the framework of perceptual independence/integration.  Participants listened to sequences of tones that contained variations in timing, intensity, or both.  Each participant tried to detect variations on the dimension that was declared relevant, which was either timing or intensity.  The irrelevant dimension was held constant, varied in a manner uncorrelated with the relevant dimension, or varied in a correlated manner.  When the variations in the two dimensions were correlated, the correlation could be either positive, that is, timing and intensity created accents in the same sequences, or negative, that is, timing and intensity created accents in different sequences.  Uncorrelated variation in the irrelevant dimension interfered with detecting variations in the relevant dimension.  In the case of a positive correlation between the two dimensions, detection of variations was better compared to the absence of variation in the irrelevant dimension only for listeners who attended to timing.  In the case of a negative correlation, the effect was in the opposite direction.  The results showed that timing and intensity accents were not processed by completely independent channels.  Rather, information from the two dimensions combined at a late stage of processing.