Joy

Joy, beautiful spark of Gods, daughter of Elysium, we enter, burning with fervor, heavenly, your sanctuary! Your magic brings together what custom has sternly divided. All men shall become brothers, wherever your gentle wings hover.
Wow. I don't know where even to begin in my testimony that the foregoing lyrics are among the most iconic in all of music. It was originally a poem written by eighteenth century German poet Friedrich Schiller; however, it was made famous by Ludwig van Beethoven, who set its German lyrics to music, and mind you, it is instantly recognizable the world over. Even to those who have never had a taste for classical music. It is the official anthem of the European Union, and it is an ode. An Ode to Joy.
Freude, schöner Götterfunken, tochter aus Elysium, wir betreten feuertrunken, himmlische, dein Heiligtum! Deine Zauber binden wieder was die Mode streng geteilt; alle Menschen werden Brüder, wo dein sanfter Flügel weilt.
If aliens from another world visited Earth, what would be the first song we play to have them understand our kind the best? My vote would go to Ode to Joy. It is encompassed within the Fourth Movement of Beethoven's Ninth Symphony. The movement starts out loud and intense, as if it would be a rambunctious finale to what was already an outstanding symphony. But then something interesting happens. The music suddenly grows very quiet, almost haltingly so. One could hear a pin drop. Extremely softly, the basses and cellos frame a few notes that would come to be the defining phrase of Beethoven's entire repertoire. The basses and cellos hand it off to the violas and french horns, who play variations of the same phrase in increasing jubilance. As the violins enter, it is very clearly realized that what started out as an intense, turbulent movement has perfectly transformed into a triumphant statement of pure happiness. The end of this gorgeous crescendo is encapsulated in a frisson-inducing, exultant culmination.

Sustained adequately, the triumph ends, and the intense atmosphere of the introduction is repeated. But right before the intensity can climax, a remarkable thing happens: a bass vocalist begins singing. In Beethoven's time, a choral symphony (one that is sung) was unprecedented. Beethoven's Ninth redefined what it means for a musical work to be a symphony. The addition of vocals was akin to having a flash mob audience. Imagine what Beethoven's contemporaries (or perhaps what you) might have thought when the orchestra stops for a random guy, who stands up at the climax of a symphonic movement and speaks this:
Oh Friends! Not these sounds! Let us instead strike up more pleasing and more joyful ones.
What? Who is this man? Why is he being so rude? In a moment you realize that this was completely intentional, that a choir was ingeniously added to give the symphony a new meaning, a new flavor. It is here where the entire choir strikes up and announces a single word: Joy.
Joy! Joy! Joy, beautiful spark of Gods, daughter of Elysium, we enter, burning with fervor, heavenly, your sanctuary! Your magic brings together what custom has sternly divided. All men shall become brothers, wherever your gentle wings hover.
Whoever has been lucky enough to become a friend to a friend, whoever has found a beloved wife, let him join our songs of praise! Yes, and anyone who can call one soul his own on this earth! Any who cannot, let them slink away from this gathering in tears!
Every creature drinks in joy at nature's breast; All Good, all Evil, follow her trail of roses. She gives us kisses and wine, a true friend, even in death; even the worm was given desire, and the cherub stands before God.
Gladly, just as His suns hurtle through the glorious universe, so you, brothers, should run your course, joyfully, like a conquering hero.
Be embraced, you millions! This kiss is for the whole world! Brothers, above the canopy of stars must dwell a loving father. Do you bow down before Him, you millions? Do you sense your Creator, o' world? Seek Him above the canopy of stars! He must dwell beyond the stars.
There are multiple accounts on this, but it has been said that at the end of the symphony's premiere, an almost-completely deaf Beethoven was still vigorously conducting--out of sync with the rest of the orchestra. He had to be physically turned around by the contralto vocalist in order to see (not hear) the tumultuous applause that erupted at the conclusion of the symphony. "According to one witness, 'the public received the musical hero with the utmost respect and sympathy, listened to his wonderful, gigantic creations with the most absorbed attention and broke out in jubilant applause, often during sections, and repeatedly at the end of them.' The whole audience acclaimed him through standing ovations five times; there were handkerchiefs in the air, hats, raised hands, so that Beethoven could at least see the ovation gestures from an audience he could not hear" (Wikipedia).

"Ode to Joy" would allow the aliens to understand that we humans are capable of expressing many emotions -- fear, anger, shame, disgust, melancholy, and that's just to name a few. But among all the emotions we can feel, one rises above the rest as what is unequivocally the best and greatest of them all. One that is shared by both good and evil. One which gives our lives meaning. One that unites the beggar and the princess. One that brings together that which custom has sternly divided. A beautiful gift sent directly from the sanctuary of divinity.

The feeling of joy.