The present study investigated simultaneous processing of language and music using visually presented sentences and auditorily presented chord sequences. Music-syntactically regular and irregular chord functions were presented synchronously with syntactically correct or incorrect words, or with words that had either a high or a low semantic cloze probability. Music-syntactically irregular chords elicited an early right anterior negativity (ERAN). Syntactically incorrect words elicited a left anterior negativity (LAN). The LAN was clearly reduced when words were presented simultaneously with music-syntactically irregular chord functions. Processing of high and low cloze-probability words as indexed by the N400 was not affected by the presentation of irregular chord functions. In a control experiment, the LAN was not affected by physically deviant tones that elicited a mismatch negativity (MMN). Results demonstrate that processing of musical syntax (as reflected in the ERAN) interacts with the processing of linguistic syntax (as reflected in the LAN), and that this interaction is not due to a general effect of deviance-related negativities that precede an LAN. Findings thus indicate a strong overlap of neural resources involved in the processing of syntax in language and music.