Music video history

Despite many artists creating videos to accompany their songs, the first official promotional music video was made by Queen for 'Bohemian Rhapsody' which was recorded in November 1975 and aired that same month. It was due to the success of the song that creating music videos to accompany songs became a trend with other artists in order to help promote their music, and it is because of this they are also referred to as promotional videos or promos.
(Wikipedia, Slideshare)

Michael Jackson is known for creating the most expensive music video ever made for the song 'Scream' which cost $7 million dollars to produce. Madonna followed close behind with 'Die Another Day' costing over $6 million and both her other songs 'Express Yourself' and 'Bedtime Story' costing $5 million. (Wikipedia)

The top viewed music videos ever on Youtube include Gangnam style by PSY (2 billion), Baby by Justin Bieber (1 billion), On the Floor by Jennifer Lopez and Pitbull (750 million), Eminem's Love the Way You Lie (709 million) and LMFAO's  Party Rock Anthem (704 million)
(Wikitubia)

There is a variety of key conventions associated with music videos such as mid shots or close ups (in order to give the artist more camera time so as to make them the centre of attention), shots of the artist, sometimes instruments and often a visualisation of the lyrics. However most of them vary based on the music's genre and style, for example:

Rap/ Hip Hop
The artists usually wear expensive branded clothing, jewellery or cars, with lots of money, objectifying women all in order to show the artist's wealth and make them look more powerful.
Their objectification of women means many of their shots follow Laura Mulvey's male gaze theory and shots tend to be quite slow paced to put more focus on the artist.

For example in 50 Cent's 'Candy Shop' in which he wears a fur coat and gold jewellery and drives a sports car. The whole music video also shows him surrounded by women seducing him, showing his voyeurism towards them.

Rock
Artists are mostly seen performing at concerts or as bands wearing casual clothing to focus their audience mostly on the music as a post to the video's content.

Commonly there are close up shots of instruments being played and, depending on the pace of song, often use fast paced editing though generally they avoid using too much editing techniques so as to focus solely on the artist.

Many of these can be seen in You me At Six's 'Lived A Lie' such as close up shots of the instruments and the artists in casual clothing.

Metal
Similarly to rock many of their music videos comprise mostly of the band performing and playing their instruments. They commonly wear lots of makeup or costumes to show themselves as individuals and standing out. Their songs tend to be very dark themed so low key lighting and fast paced editing is used to give a sense of fear and tension to the viewer.
An example of some of these is in Metallica's video for 'Until It Sleeps' which includes performance shots, costumes and makeup and the dark theme.

Music video comparison
I made a comparison between an old music video with one of the most recent ones to see the differences in the two. I compared Queen's Bohemian Rhapsody with PSY's Hangover. Firstly I found there was a much larger variety of shots in the newer video and much more editing used. There was also a much clearer narrative in the newer one and link between the visuals and lyrics and better lip syncing, whereas the older music video included mostly performance shots of the artist. There is a much more artistic look to the older video in comparison to the newer one as well, which would relate to the artist's need for promotion.

Because these two artists were of very different genres I realised it may affect how their differences appeared so I decided to compare another two music videos with the same genre which were ACDC's "Highway To Hell" and My Chemical Romance's (MCR)"Teenagers", both of which are Rock videos. My first clear finding and one which is the same difference as what I found in the other two videos is how ACDC's video lacks a narrative unlike MCR's video which portrays a school of rebellious teenagers watching the band's live performance in a school hall. These visuals relate with the lyrics of the song which ACDC's video doesn't do either. However the clear similarity between the two despite this is in both videos the artist are shown performing live on a stage which is of course a generic convention of Rock videos. Similarly, the two videos also contain quite low key lighting which highlights the stage lights on their stage more to give a bigger sense they're performing live. In terms of editing and camera work, MCR's newer video contains not only much faster paced editing but also faster camera movement and a larger variation of camera angles in each of their shots, which could be partly due to the narrative layout of the video. However, like in many music video's, the camera focuses most of its shots on the main artist, more specifically the lead singer of each band, in both videos. Finally, the background dancers and teenage crowd are featured in the video as extra characters in the newer music video, as well as the band itself, linking back to the fact that they use a narrative structure which usually would require additional characters to interact with the artist.