The answer – in part – seems to be that the patterns of pitches in major keys mirror those of excited speech, whereas minor keys parallel subdued speech. That suggests that language shaped our musical expression of emotion.
Several factors affect music’s sentimental influence, and some are common sense: a fast, loud, jumpy rhythm sounds happy because it reflects the way an excited person behaves, and slow, quiet music with a regular beat mimics a mournful emotional state.
What’s less obvious is why tunes in major keys tend to sound cheerful, whereas those in minor keys sound sad. “This is an age-old problem in music theory,” says Daniel Bowling, a neuroscientist at Duke University in Durham, North Carolina, who suspected emotional speech patterns might be behind the link.