Out of the 12 all-time most viewed YouTube clips, nine are professionally made music videos, and at least one rock video has been watched more than 75 million times.

But despite this, musicians are claiming that they are still waiting for any revenue from the Google-owned video sharing site.

In the deals struck with the record companies, starting with Warner Music Group in September 2006, YouTube agreed to pay the labels for use of sound recordings and to also "share revenue generated from playbacks", according to YouTube.

The company did not provide financial details of the agreements.

But top music managers have told CNET News that their clients haven't seen any money from the licensing deals the four largest music labels have signed with YouTube over the past 18 months.

"I don't know any artist who has gotten a royalty statement (from their label that includes YouTube money)", said music attorney Chris Castle.

YouTube, however, is claiming that it has been collecting money, and this has been going to record labels.

So why isn;t money reaching the artists themselves?

According to CNET, several music managers say that YouTube's filtering system is unable to accurately track videos featuring copyrighted songs uploaded to the site by users, and without an accurate accounting of the music, labels can't compensate artists fairly.

There have also been reports of "lags in reporting" because of technology problems at the video site.

But some, to counter the concerns, are urging patience.

One source told CNET: "These are still early days. The music managers are always quick to demand money or to shut down a service or to file suit. Sure, maybe down the road the labels will have to flex their muscles but right now they want to give YouTube some time to develop".

And some add that it is the responsibility of the music labels to make sure that fees reach the artists - and so it is not YouTube's problem at all.

But record labels claim they are doing everything they can.

Warner Music told CNET: "Warner Music Group shares all of the digital revenue we receive with our artists in accordance with the terms of their agreements", the company said in a statement.

"While those agreements are confidential, they outline a reporting and payment process to which we strictly adhere."

The other three labels declined to comment.