There are songs, and then there are dances. Here’s a song-and-dance routine that, according to one of the lawyers involved, could amount to a billion-dollar lawsuit against YouTube.

Through a new outfit called Global Music Rights, music industry heavyweight Irving Azoff manages the performance rights of some 20,000 songs including works composed by the Eagles, Pharrell Williams, John Lennon and others. Many of the songs were previously handled by ASCAP and BMI, which thanks to consent decrees with the Justice Department, were subject to blanket licenses anytime a digital outlet like YouTube requested one. Not anymore.

And now the dance.

Azoff has informed YouTube that it lacks performance rights for these 20,000 songs — including ones by Smokey Robinson, Chris Cornell, and George and Ira Gershwin. Since November, when YouTube announced the coming launch of a subscription service to compete with Spotify and Pandora, Azoff has kept up the pressure to license, but Google isn’t backing down.

That’s quite upsetting to Azoff, who is prepared to launch an all-out legal war if negotiations don’t prove fruitful and if YouTube refuses to remove the works. Why YouTube and not, say, Spotify? “Because they are the ones that have been least cooperative and the company our clients feel are the worst offenders,” Azoff tells The Hollywood Reporter. “It’s also their attitude.”

The dance, whether this be a tango or waltz, is more than a basic two-step.

For example, maybe YouTube actually has rights to perform these 20,000 songs. PROs like ASCAP and BMI often issue multi-year licenses, and just because a songwriter withdraws in the middle of a licensing term doesn’t mean that the licensee loses rights until the expiration of the term. But neither YouTube nor ASCAP are letting Don Henley, Pharrell Williams and their reps know the situation, according to GMR attorney Howard King.

In a letter sent earlier this month to YouTube, King writes, “Without providing a shred of documentation, you blithely proffer that YouTube can ignore the Notices because it operates under blanket licenses from performing rights organizations other than Global. However, you refuse to provide the details of any such license agreements, presumably because no such agreements exist for YouTube’s present uses of the Songs in any service, but certainly with respect to its recently added Music Key service.”

Proving rights would hardly end this dance.

Although YouTube has enacted anti-piracy measures since the video site’s early days a decade ago, some things haven’t changed much at all: Copyright holders insist that it’s Google’s responsibility to get a license while Google respond that the onus is upon rights-holders to tell it what specifically to remove. In other words, is the use of copyrighted works online opt-in or opt-out?

On Dec. 4, Google lawyer David Kramer responded to King’sletter with one of his own attacking a “misguided” legal position. “This is now your third attempt to circumvent the straightforward DMCA notice-and-takedown process that Congress devised to handle situations like this,” writesKramer,  a partner at Wilson Sonsini

According to Kramer’s letter, GMR must not only submit a statement under penalty of perjury that it is authorized to act on behalf of the owner, and not only identify the works at issue, but also identify URLs where infringing material resides. That would mean sending lots of takedown notices over some 20,000 songs being used in probably hundreds of thousands of videos.

“It is disingenuous that they can keep their hands over eyes until we tell them the URL,” King tells THR. “They know where it is. We don’t want this to become whack-a-mole.”

King points to ContentID, YouTube’s digital fingerprinting technology that advertises itself as a system by which copyright holders can “easily identify and manage their content on YouTube,” a system where “copyright owners get to decide what happens when content in a video on YouTube matches a work they own.”

ContentID has paid out more than a billion dollars since inception, but is it purely a monetization tool or can it be used by songwriters like Pharrell Williams to remove unlicensed material? King believes that YouTube has been holding ContentID out to be the latter — which he says means that YouTube “can find sound recording by The Eagles and program it [to remove] in a millisecond.”

In the absence of doing so, King asserts that YouTube loses its safe harbor under the Digital Millennium Copyright Act because it has actual knowledge of infringing activities, or at least, awareness of facts or circumstances where infringing activity is apparent. YouTube disputes this position — it previously went several rounds with Viacom over the matter, and so-called “red flag awareness” will also be addressed again soon by the 2nd Circuit Court of Appeals.

In the meantime, both sides will continue their posture until someone decides to end the pre-litigation dance.

“This will result in someone blinking, and if it is not them, there will be a billion dollar copyright infringement lawsuit filed,” says King, still hopeful that it won’t end up in court, but warning that YouTube’s “music service will be adversely impacted if they let this go to adjudication. It seems silly that they would let this be test case.”

The back-and-forth letters by the lawyers involved in the battle are below.