Purpose of a music promo video

Music videos are used to promote the artist and their music single and album. Music videos enable companies to make money and increase their sales; as they persuade the audience to purchase their music. This raises the audience awareness or profile of the artist/group.

Synergy 

However, music videos are just a small part of the multimedia campaign. 
Radio, Print Media, New Media, Film and TV are also used.

One of the most popular forms of synergy with music videos are films. 
There are many types of synergy that can be made with music videos. For example there is product placement music video synergy. This can be clearly seen in Miley Cyrus' video where she promotes a Beats Pill.

Another interesting example involves Aziatix and their synergy for the Toyato Corolla (car). This music video not only promotes the car and gives it a cool image but also promotes the group.





Bryan Adams (Everything I do) I do it for you
For film -  Robin Hood:Prince of Thieves. 
The film went on to becoming the second highest grossing film of its release year. The song spent sixteen weeks at number one on the UK singles chart and was also an enormous chart success becoming one of the best selling singles of all time.

Wet Wet Wet - Love is all around
Four Weddings and A Funeral 
It was a huge international success and spent fifteen weeks atop the British charts. The song increased the film's popularity and revenue. 

The music video features white screens on which clips from the singers and film alternate. 

Elton John - Can you feel the love tonight
Soundtrack for The Lion King 
Gained popularity for the artist and the film, proven by the numerous awards won including Golden Globe, Academy Award, Grammy awards.



Whitney Houston - I will always love you
The BodyGuard 
The song charted in numerous countries for several weeks and even took the record from Bryan Adam's Everything I do, I do it for you. 

Eminem  - Lose yourself
8Mile
First rap song to win Academy Award for best original song



International example:

Another example of synergy with music videos are Korean Dramas. 
OSTs are used as the drama soundtrack and promote both the artist and drama. 
This music video for the song "stand up" features clips of the drama "To The Beautiful You"as well as the artist J-Min performing the song.