3. Music video..

A music video is the illustration to song lyrics. Used in various ways: to promote a song, to entertain, to give a varied audience a better understanding of a song and to establish the artists image. As well as that, music videos can help give the artist a better perspective of their song.
Music videos aren't as straight forward as one would think; there's more to filming a music video.

For example Katy Perry's video for Last Friday Night. This music video tells a narrative and was a great mode of promotion for the song, with the 5 million views the video received it became very well known. Gave her audience great entertainment.