Caprice

A Caprice in painting is an architectural fantasy, and in music, it means a free-form, lively piece of music. It's taken directly from the Italian word for them, capriccio.

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So you can also see this as a musical name, like Harmony or Melody.

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Tchaikovsky has a beautiful piece of music, which in English is called "Italian Caprice".

Actually, this means "impulse" or "fickle act" in French, not Italian. The Italian word is "capriccio". Either way, the implications of this name are more negative than positive. [noted -ed]

"Caprice" is also an English noun. A caprice is a sudden whim or fancy.