Which one is the prior? content or medium?

new media: determining or determined? 2 (Dec 6)

1.6.3 Williams and the social shaping of technology
1.6.4 the many virtues of Sant McLuhan

There were two view points.
First one is that contents should be change to express medium.
The other is that let contents leave originally, we chage medium.
I will give a example about "music video"
We can define the content is the song and medium is the music-video.
When Sungmo Cho's music video came out, it was sensation.
Because we saw like a movie, which made well.
However, the problem is that we didn't recongnize music at first.
Because the image is more stimulating the nerves system than music.

There is the song, that' why music-video made.
However we more care about music-video than the song.

In other way, there is a music-video, that' why the song was popular.
Which one is the first??