Repetitive sound sequences are easily distinguished from other background sounds. The present study investigated the neural mechanisms underlying the perception of repetitive sound sequences. We measured neural responses at the layer IV in auditory cortex of anesthetized rats and compared evoked responses to repetitive tone sequences and those to random tone sequences. Our results demonstrated that repetition of tone sequences modulated both amplitude and band-specific phase coherence of auditory evoked responses. The amplitude of evoked responses depended on a preceding tone in a given sequence, possibly due to the forward masking. The phase coherence tended to be higher during the repetitive sequences than during random sequences, specifically in the low-gamma band. The enhancement of amplitude to a specific tone was associated with an increase of phase coherence in the low gamma band. Thus, the co-modulation of amplitude and phase coherence of evoked responses plays an important role in perception of sound regularity.