As Burning Down said, music is "an art form consisting of sequences of sounds in time,
esp tones of definite pitch organized melodically, harmonically, rhythmically and according to tone color."
So music, generally speaking, is a planned sound event.
A Tune is "a succession of musical sounds forming an air or melody, with or without the harmony accompanying it."
According to that definition, it's just the main melody of music, without any accompanying instruments.
The definition for noise is "a nonharmonious or discordant group of sounds."
Actually, noise, if it's not planned, will be just noise and no music.
Jazz artists for example don't write sheet-music mostly, but think ahead right in the moment of playing.
I would say noise is sound that happens without a purpose, because sometimes discordant sounds are wanted in music.
The source of the definitions is Dictionary.com
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