Pandora (P) would like more time. But investors are growing impatient.

Shares of the world's largest internet radio service tumbled Friday morning after would-be merger partner Sirius XM (SIRI) - Get Sirius XM Holdings, Inc. Report , gave every indication that it's not focused on a company-changing merger or acquisition. Pandora's stock has been lifted at various points over the past year on speculation that Sirius, the satellite-radio operator controlled by billionaire media mogul John Malone, had delivered a buyout offer.

"With respect to all the chatter about acquisitions, you have to look at them as sort of being not very likely," Sirius CFO David Frear said Thursday after the close of trading at the Citi Internet, Media & Telecommunications Conference in Las Vegas.

On Frear's comment, Pandora shares were down 5.2% on Friday to $12.33. Pandora declined to offer a rebuttal. 

TheStreet Recommends

For Pandora, these are times of high expectations following a year in which the stock stood largely in place -- dropping 2.8% -- and the company reported losses of more than $250 million.

Co-founder and CEO Tim Westergren, who returned to Pandora's top job in March, is pushing to roll out the company's on-demand music service, Pandora Premium, sometime this quarter. The service is viewed as a complement to Pandora's free, ad-supported radio service that plays songs based on a user's musical preferences.

With an eye toward growing revenue, Westergren also orchestrated a series of executive changes in the fourth quarter that included the resignation last month of Sara Clemens as chief operating officer and Mike Herring's impending move from finance chief to a strategy-focused position as president, once a CFO replacement is found.

Yet it's Pandora Premium that Westergren is betting will help it reverse a decline in total users -- 77.9 million at the end of the third quarter, compared with 78.1 million during the same period a year earlier -- that has heightened investor concern about the company's long-term health.

Frear poured salt on his earlier comments by suggesting that Pandora may be wrong to enter into the on-demand music market, dominated by Spotify and Apple (AAPL) - Get Apple Inc. (AAPL) Report Music and with an aggressive new player in Amazon (AMZN) - Get, Inc. Report Prime and its voice-activated Alexa device.

"And you know on the Pandora front, they've got a big change in strategy with this move into the interactive sort of music business, which we've been public in our doubts about it. And we'll see how that strategy plays out for them."