Do different music channels have different target audiences?

Yes, for example capital radio TV have a target audience of 12-30 as these are the people that listen to the type of music they play. 12 would be the minimum age as anyone younger wouldn't be in charge of the TV, or may have their own.  

Where can audiences watch music videos:

Music TV channels, YouTube, Facebook, Vimeo, Twitter, etc. YouTube and Facebook are by far the biggest platforms to watch music videos on and reach the largest audiences.
Films are increasingly available 'on demand' because less people are going out to rental shops or cinemas and want to watch it at home in their own comfort.
Smartphones, games consoles (Xbox one) ,and smart TV's all allow streaming on demand and to watch YouTube on them.