Serenade... it's the ultimately romantical piece of music aiming to express one's feelings towards his/her beloved in a perfectly poetical way by describing allegorically how beautiful he/she is and how uncommonly sublime their love is.
Originally serenades were performed by European minstrels accompanied by soloing mandoline, lute, guitar, fiddle or viola. The tunes they played were simple yet melodical; the lyrics they sung was heartfelt and figurative.
Many centuries passed and serenades are still as actual as they used to be, because basically the romantic feeling of love is appropriate in any epochs and cultures.
Thanks to technical evolution a number of superb musical instruments way more powerful than mandolines are available and many various musical styles were developed, and depending on musical preferences of your beloved you can present it as a piece of r&b, rap, rock, pop, classics, blues or jazz.
If the window of your beloved is not that close to the ground as it