Warner Music Group investors were singing a new tune yesterday following a report by The Post that the company’s private-equity backers are considering taking the company private for a second time.

Shares in the stock surged 21 percent to close at $12 after hitting a new all-time low of $9.79 on Tuesday.

Also aiding Warner: Citigroup analyst Jason Bazinet yesterday upgraded his rating on the stock to a “buy” calling the company’s current share price undervalued given its cash flow performance. He thinks it is worth $13.

Bazinet says the recent haircut Warner has taken in the stock market has created “more realistic investor expectations” for the company.

Word of a potential second go-around for WMG as a private company surfaced Tuesday after its stock was pummeled over its mixed third-quarter results.

The music giant’s frustrated financial backers – a consortium led by Thomas H. Lee, Bain Capital and Providence Equity Partners – think the stock should be trading between $18 and $20, not $10, sources said.

At the very least, these sources said they expected Warner’s stock price to rebound to around $14 after it withdrew from the EMI auction.

But the going-private discussion is understood to be in its infancy. Ultimately the company may elect to remain on the public markets.

The company is also mulling other options ranging from a stock buyback to a securitization deal for its music publishing assets, sources said.

Bishop Cheen, an analyst with Wachovia, said at current valuations it will be more expensive to take Warner private a second time.

brian.garrity@nypost.com