dissonance
A combination of notes that creates tension and a sense of instability.
In Depth
Dissonance is the sense of tension or instability created when certain notes sound together. Intervals like the minor second, major seventh, and tritone are traditionally considered dissonant because they create an acoustic roughness that the ear perceives as unresolved.
Dissonance is not inherently bad — it is essential to musical expression. Without tension, there can be no resolution, and without resolution, music lacks direction. The history of Western music can be traced through the gradual acceptance of previously dissonant sounds as consonant. What shocked audiences in Wagner's time is now standard in jazz and pop harmony.
When Stravinsky's Rite of Spring premiered in 1913, the extreme dissonances caused a near-riot in the audience. Within a decade, the same music was considered a masterpiece.