What is the definition of the musical term key

In music theory, the key of a piece is the group of pitches, or scale that form the basis of a music composition in classical, Western art, and Western pop music.

In music theory, the key of a piece is the group of pitches, or scale that form the basis of a music composition in classical, Western art, and Western pop music. ... Notes and chords other than the tonic in a piece create varying degrees of tension, resolved when the tonic note or chord returns.

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What are the choices