In a major changing of the guard in the music biz, self-made multibillionaire Len Blavatnik’s Access Industries has agreed to acquire Warner Music Group for $3.3 billion in cash, WMG announced Friday.

Price boils down to $8.25 per share, representing a 34.4% premium over the average share price of $6.14 during the last six months.

WMG estimated that the deal, which must be approved by federal regulators, would be completed by the end of the third calendar quarter.

Agreement reps a solid payoff for WMG chairman-CEO Edgar Bronfman Jr. and his equity partners, who purchased the music company from Time Warner in 2004 for $2.6 billion and took it public in 2005.

Bronfman said in a statement, “We believe this transaction is an exceptional value-maximizing opportunity that serves the best interests of stockholders as well as the best interests of music fans, our recording artists and songwriters, and the wonderful people of this company. We are delighted that Access will be the new steward of this outstanding business. They are supportive of the company’s vision, growth strategy and artists, while bringing a fresh entrepreneurial perspective and expertise in technology and media.”

In the end, after more than three months on the market and three rounds of bidding, WMG’s owners — Bronfman and equity firms Thomas H. Lee Partners and Bain Capital — opted for a deep-pocketed buyer with cash on hand and spurned offers from other entertainment biz concerns.

Sony Music Entertainment’s publishing arm Sony/ATV, Universal Music Group, BMG Rights Management — a joint venture of German publishing giant Bertelsmann (formerly partnered with Sony Corp. in Sony BMG) and equity firm Kohlberg Kravis & Roberts — and Live Nation Entertainment were said to be interested in the company.

However, regulatory concerns — which scuttled more than one attempt to merge WMG with EMI Music, the most recent of which came in 2006 — apparently scotched the bids by the music units.

Companies controlled by other high-flying financial players — brothers Tom and Alec Gores, Ron Burkle, Ron Perelman — were purportedly keen on acquiring WMG, but Blavatnik’s close association with WMG and Bronfman evidently trumped their bids.

Blavatnik, 53, controls a fortune estimated by Forbes, which lists him as the 80th richest man in the world, at $10.1 billion. The lion’s share of his wealth comes from Access Industries’ investments in petrochemical firms (TNK-BP, LyondellBasell) and aluminum production (UC RUSAL).

His media holdings are far less significant: Access’ portfolio includes telcos, wireless and mobile operators, Russian and Israeli TV production units and the U.K. operations of Mel Gibson and Bruce Davey’s Icon Group.

However, Blavatnik, like Bronfman — who was a top exec with his family’s Seagram distillery before buying into UMG and then WMG — is not immune to the allure of showbiz. Last year, Access bid on MGM’s assets but pulled out of the deal; Blavatnik later invested $25 million in the Weinstein Co.’s film fund, which finances lower-budgeted pics.

Access controlled an estimated 2% interest in WMG before the purchase. Blavatnik is no stranger to the music firm and Bronfman: He held a WMG board seat for four years and invested an estimated $25 million in the company. In 2007, Blavatnik bought a Manhattan property from Bronfman for $50 million.

Blavatnik said in a statement, “I am excited to extend my longstanding involvement with Warner Music. It is a great company with a strong heritage and home to many exceptional artists. I look forward to working closely with the many talented people within the company.”

While the music mogul and the Russia-born entrepreneur are said to be close, the Wall Street Journal reported late last month that Blavatnik had threatened to pull out of the bidding for WMG as the auction process dragged on.

Though all signals point to continuity, it still remains to be seen if Bronfman and his exec team — led by vice chairman Lyor Cohen, who also serves as chairman-CEO of recorded music for North America and the U.K. — will remain in place after the acquisition receives SEC approval.

Under Bronfman, WMG has seen deepening losses during music’s industrywide tailspin. According to the company’s most recent annual report, for the fiscal year ended Sept. 30, the firm showed a decline in revenues for four of the last five years, dipping to $2.98 billion in 2010. Its net losses have increased steadily year to year, from $21 million in fiscal 2007 to $143 million in 2010.

According to Nielsen SoundScan, WMG was third among the four majors in total album market share last year with 20% (down from 20.5% in 2009), trailing UMG (30.8%) and SME (27.9%). It failed to place a single album among the top 10 bestsellers of the year.

Reflecting the company’s unstable commercial outlook, flagship label Warner Bros. Records’ longtime chairman/CEO Tom Whalley exited in September, and Rob Cavallo, previously WMG’s chief creative officer, was installed as chairman (Variety, Sept. 15).

With Bronfman aboard, WMG could make another pass at an acquisition of No. 4 major EMI. Since February, the debt-distressed company has been in the hands of its principal lender Citigroup, which is expected to put EMI on the block formally within weeks. Bronfman is known to have long coveted the London-based company; he made overtures to merge it with UMG, then owned by Seagram, in 1998.

The New York Times’ initial report of WMG’s enlistment of Goldman Sachs to shop the company also noted that a purchase of some or all of EMI’s assets was also considered a possibility (Variety, Jan. 21).

WMG’s stock, which had languished under $6 per share for six months before the company was put on the block in January, leaped to a 52-week high of $8.18 in Friday trading on the New York Stock Exchange.