Music finds a comfortable parallel with that of human language. Much as language has words, sentences, and stories, music has tones, melodies, and songs. The theory of music emphasizes the elements from which music is composed. One such structure is the melody, which is a grouping of musical notes that combine into a basic, but immensely flexible structure. Another is the chord, which is two or more notes played simultaneously to create a harmony. The impact of music throughout history can be clearly seen, as both entertainment and an art.