Results from functional imaging and electrophysiology suggest that responses in auditory cortex can be modulated by stimulation of other sensory modalities. In fact, auditory responses of neurons in primary and secondary fields are enhanced or reduced by the simultaneous presentation of visual or touch stimuli. Although often denoted as sensory integration, the exact function of these multisensory influences is unclear, and it the auditory neurons more reliable or informative about the acoustic environment. To scrutinize the neuronal basis of these multisensory influences, we investigate mechanisms of neural information coding in the auditory cortex of the macaque. For just acoustic stimulation, we find that temporal neural codes, such as precise spike timing, or the relative firing of neurons to background activity (phase of slow field potentials) provide considerably more information than firing rates. In addition, these different codes can encode complementary information about the same stimulus epochs. Overall, this suggests that the auditory cortex might rely on the use of several neural codes operating on different spatial temporal scales at the same time. In the context of multisensory stimuli, we find that neurons become more informative about the stimulus when an auditory stimulus is complemented with the matching movie. Especially the information in firing rates benefits from the visual stimulation, while spike times show a rather small information gain. In addition we find that this information gain by multisensory stimulation is not uniformly distributed across all stimuli, but is highest for those stimuli which elicit strong responses. Overall our findings suggest that visual influences in auditory cortex might be more than just a simple response modulation, but make neuronal firing more reliable, and hence enhance the information encoded in auditory cortex about the environment.