Spatial congruity effects are often interpreted as evidence for metaphorical thinking, but an alternative markedness-based account challenges this view. Here, we compared metaphor and markedness explanations for spatial congruity effects, using musical pitch as a testbed. English speakers who talk about pitch in terms of spatial height were tested in space-pitch compatibility tasks. To determine whether congruency effects could be elicited by any marked spatial continuum, participants classified pitches as 'high' and 'low' or as 'front' and 'back' (both pairs of terms represent marked continuums). We found congruency effects in high/low conditions but not in front/back conditions, indicating that markedness cannot explain congruity effects. A second experiment showed that congruency effects were specific to spatial words that cued a vertical schema (tall/short), and that congruity effects were not based on polysemy (e.g., 'high' referring both to space and pitch). Together, these results suggest that congruency effects reveal metaphors, not markedness.