Synchronizing finger movements with the motion of a visual target is especially successful when tapping downward with a downward-moving stimulus. One explanation is that the directional compatibility of stimulus movement (downward) and synchronized action (downward) enhances the synchronization performance. Another is that the performance is enhanced by the directional compatibility of stimulus movement (downward) and gravity (downward). This study separated effects of stimulus-response compatibility (SRC) and stimulus-gravity compatibility (SGC) by manipulating both the stimulus movement direction and the tapping direction. Results showed a robust effect of SGC on the synchronization performance—that is, more directional compatibility between stimulus movement—and gravity yielded more stable synchronization. SRC also influenced the performance, although this effect was only pronounced in fast sequences. The SGC effect suggests that the brain can exploit prior knowledge of gravity direction to enhance timing in visuomotor synchronization. The SRC effect suggests that the coding of visual events and synchronized actions might operate in a common representational medium, and the influence of sequence rate might reflect the rate limitation of information transfer from the visual system to motor system.