We examined effects of tempo and mode on spatial ability, arousal, and mood. A Mozart sonata was performed by a skilled pianist and recorded as a MIDI file. The file was edited to produce four versions that varied in tempo (fast or slow) and mode (major or minor). Participants listened to a single version and completed measures of spatial ability, arousal, and mood. Performance on the spatial task was superior after listening to music at a fast rather than a slow tempo, and when the music was presented in major rather than minor mode. Tempo manipulations affected arousal but not mood, whereas mode manipulations affected mood but not arousal. Changes in arousal and mood paralleled variation on the spatial task. The findings are consistent with the view that the "Mozart effect" is a consequence of changes in arousal and mood.