NEW YORK (TheStreet) -- Pandora Media (P) stock is gaining 5.56% to $10.54 on heavy trading volume Tuesday afternoon after Corvex Management, a hedge fund run by Keith Meister, disclosed a 10% share in the music streaming service.

On Monday, Meister sent a letter to Pandora Chairman Jim Feuille and the board urging the company to sell itself.

"Simply put, we believe Pandora can become an even more differentiated product and a more valuable business as a part of a larger enterprise," Meister said in the letter.

Meister argued that Pandora's user base, engagement and song recommendation engine are assets that could be further developed and monetized at a larger company.

Corvex's move has ignited speculation that Apple (AAPL) could be a potential buyer, but TheStreet's Jim Cramer, portfolio manager of the Action Alerts PLUS charitable trust, believes Apple is more likely to be the end of Pandora, not its savior.

"I think Pandora could be bought by somebody, but I don't expect Apple to bail them out," Cramer explained.

So far today, 21.54 million shares of Pandora Media have been traded, more than double its average daily volume of 9.08 million shares.

Separately, Pandora Media has a "sell" rating and a letter grade of D at TheStreet Ratings because of the company's deteriorating net income, disappointing return on equity, poor profit margins, weak operating cash flow and generally disappointing stock performance.

You can view the full analysis from the report here: P

TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this article's author.

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