Franz Schubert's life:
Franz Schubert was born in Vienna, Austria in 1797 as the Classical era was beginning to come to an end. His father was a schoolmaster, and he was Schubert's first teacher, teaching Schubert to play the violin and the piano in his childhood. Schubert then began playing the Viola, and his gifted voice earned him admittance to the Imperial Chapel choir school. There, Antonio Salieri taught Schubert theory and composition, helping cultivate a natural talent. In his late teens Schubert began to write songs, slowly learning the life of a freelance musician. While his works were brilliant he wasn't widely acknowledged as a composer, forcing him to sell his masterpieces at low prices just enough to remain alive. While he lived in poverty, he had stints working for the Esterhazy family in Hungary, and his music was greatly appreciated by his friends. So much so that the Sonnleithner family began to host evenings called Schubertiades, where Schubert's music was played and appreciated by a small circle of good friends. Yet Schubert's health deteriorated quickly, and he began to suffer from syphilis. While he died at the relatively young age of 31, he visited a man who greatly influenced, Ludwig van Beethoven on his deathbed. Schubert suffered his poverty a great deal, and after his death his possessions were merely a few clothes, a bed, and his music. Schubert's music wasn't a small amount. Schubert wrote over 600 lieder (German art songs, more below), 9 symphonies, 15 string quartets, and hundreds of other different genres of pieces including operas, masses, and piano works. But the total value of his possessions weren't enough to pay for his funeral, therefore his brother Ferdinand had to pay for his funeral.
Schubert was greatly influenced by a number of people. While Mozart and Beethoven were his idols musically, Schubert was very influenced by German romantic poets, especially Johann Wolfgang von Goethe. Schubert was so greatly influenced by Goethe that he decided to put the poet's legendary poem "Der Erlkönig" with music.
Schubert wrote it in the form of a Lied (plural: Lieder). A lied is a German art song for solo voice, often with a piano accompaniment. The lied flourished in the 19th century, partially due to the large amount of lieder written by Schubert and other German composers.
What is "Der Erlkönig"?
The Erlkönig is a malevolent creature depicted in many German, Danish, and ancient Scandinavian poems and stories. In some he is like a god of death, coming to the people in their deathbed as a confirmation of their impending doom. But the Erlkönig is more often described as an evil creature which inhabits forests and tries to lure travellers to their death, like in Goethe's poem. In many poems and stories the Erlkönig's daughters are evil forces which lure people, and there is a reference to the Erlkönig's daughters in Goethe's poem.
Franz Schubert's Erlkönig
The Erlkönig tells the tragic story of a father and son, riding through tempestuous winds on horseback at night. We hear this right away with the piano's vigorous stamping triplet octaves in t right hand, accompanied by a dark and sinister melody in the left. As they ride the father keeps his son warm in the crook of his arm, but he sees his son hides his face anxiously. When he asks what is wrong, the boy tells his father, "Father, do you not see the Erlkönig? The Erlkönig with crown and cloak?". The father reassures the child, telling him that it's a mere wisp of fog.
Schubert makes sure that the father's words are pitched in the lower register, and makes the phrases legato and smooth as the father attempts to calm the child. Meanwhile the boy's voice is in the upper register, suggesting youth and innocence along with fear.
Then the piano quietens into a soft and lovely accompaniment to the Erlkönig's voice. We hear the sweet and luring voice of the Erlkönig, telling the child of games they'll play and the golden robes his mother wears, hoping to convince the child to come with him. Yet the child is not fooled by the Erlkönig's charming voice, and instead turns to his father and calls him in fear. This is when the tempestuous right hand returns and accompanies the boy's rising cry of "Mein Vater, mein Vater!" which translates to "My father, my father!". The child tells his father of the Erlkönig's promises, and the father tells the boy to calm himself, as it's only the wind rustling through dry leaves.
Now we hear the Erlkönig again with his insincere voice which attempts to lead the boy. The Erlkönig mentions his daughters which will lead nightly dances and rock and sing him to sleep. This terrorises the son further, and he cries for his father again, a semitone higher than the last time to emit a sense of true panic. He tells his father "can't you see there, the Erlkönig's daughters in the shadows?", the father simply and soothingly replies, "My son, my son, I see it well: the old willows they shimmer so grey.".
Now the Erlkönig's final verse comes, and we see his true sinister nature. While he begins complimenting the boy to lure him, he then threatens him in the last line, where his voice lowers and darkens to a furious roar. Here's the Erlkönig's final verse: Schubert accompanies the last line with a sudden flurry of dark chords, as the Erlkönig tries to take away the child. The child screams last words to his father, and they're the highest sung yet to indicate the culmination of fear and panic in the child as the Erlkönig hath touched him. He yells the characteristic "My father, my father!" before saying, "He's grabbing me now! The Erlkönig has hurt me!".
Now we only hear the narrator, depicting the father's quick riding as he holds his moaning child in his arms. When he finally clears the forest and the courtyard, in his arms he finds his son dead. Some think that throughout the poem the father actually couldn't see the Erlkönig, and that's why he was reassuring his child so freely, but that doesn't seem the case. On the other hand, it seems more likely that the father saw the Erlkönig, but was powerless to stop the creature's assailing, and so he tried to make the last moments of his child's life more pleasant by telling him that the Erlkönig wasn't there.
There are many musical interpretations of Goethe's Erlkönig, but Schubert's is the best known. My favorite rendition is Dietrich Fischer-Dieskau's which is above. Dietrich Fischer-Dieskau does a brilliant job of telling the story, from the fearful child to the creepy Erlkönig. There are many others you can find on Youtube, and I highly recommend you to listen to a few.