Universal's premium music-video service, Vevo, looks to be getting a little more popular. Sony Music has announced that it will be joining the website, making it the second major label to join.

Although it hasn't launched yet, Vevo purports to be a legitimized YouTube, where only content-holders are permitted to upload content. As previously reported, it aims to open later this year.

Financial terms of Sony's involvement haven't been disclosed, however CEO Rolf Schmidt-Holz said: "We share a common vision of offering music videos and other premium video content from some of the world's greatest artists in an attractive, clean and intuitive environment that appeals to fans and advertisers alike".

Warner and EMI are still uninvolved, as are legions of independent labels across the world. Together, that means 53% of the market is missing. Without their presence on the service, it seems unlikely that Vevo will really be able to take off in a big way.