How have music videos changed over the years, Firstly we need to know what is the purpose of of a music video.

The purpose of a music video is to sell the song and to invoke a reaction so it leaves the audience remembering the song, it gives the listener a better under understanding  of the song. to entertain (to show off other talents),the musician may have for example dancing or acting to sell cd's and dvd's to the  viewers, to create a memorable visual for the song increasing it's chances to sell and marketing for the purposes of exposures and expansion of the artist's profile (reasons from www.slideshare.net).

Secondly,the first era of music was during (1902-1917),this was formally known as "the Phonoscene era", phonoscene was introduced to london in 1907 when Buckingham palace got it on april 4th 1907.

During 1926-1959, talkies came on to the scene, they were produced for musical short films, warner bros produced a similar thing known as the "Vitaphone" (first national stock from 1926 to 1931), the last major analog "sound on a disc system".

Thirdly the way music video's were performed was that the artist or musician would have to perform it live on stage up until 1982 when the song "thriller" by michael jackson (1958-2009). The song thriller was the first music video to be recorded that has a story behind it. But before that happend, artists would be performing their songs live without a music video, they would be performing their shows on shows like Top of the pops. For example the song "you really got me", produced and originally sung by The Kinks then later through the years another version was done by american hard rock band Van Halen in the year 1978 for their first album Van Halen along with other tracks such as eruption.