As children, we were surrounded by a word-rich environment full of sounds. Sometimes we heard the voices of our parents, the radio, or TV; other times we heard the cadences of song, where rhythm and instruments met sounds and syllables. As a language learner, it can help to think of yourself as an infant again, creating a word-rich environment for yourself that includes songs.
I encourage language students to listen to songs because:
1) It's fun. You've got to be motivated to learn!
2) You learn slang words because the language comes from a real-world source, not a textbook-manufactured source.
3) You will implicitly learn about the source culture as you absorb the meaning of the song and who the artist is.
4) It's a great way to learn new vocabulary, which you can often deduce from context clues.
5) And perhaps the best reason: you will learn how to differentiate between the various sounds (phonemes) that make up words.
Give a song a try! For Spanish language-learners, I recommend the great spring-time song De Colores.