OAKLAND — So many listeners have turned off Pandora that Friday could have been called the day the music died for the internet radio streaming pioneer.

Late Thursday, Pandora said it ended its third quarter with 73.7 million active listeners, a decline of more than 7 million listeners from the 81 million it had in the same quarter a year ago.

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Declining listener numbers, along with weaker-than-expected advertising revenue and a disappointing fourth-quarter forecast, had investors tuning Pandora out on Friday, as the company’s shares fell by almost 25 percent, to close at $5.59.

Pandora still has more listeners than Apple Music, which has 27 million paying subscribers. But the Oakland-based music streaming business trails its other major rival, Spotify, which has 140 million active listeners, including 60 million who pay a monthly fee for on-demand streaming and to avoid listening to commercials with their music.

Pandora only launched Pandora Premium, its $9.99-a-month on-demand music-streaming option, in March. The company said it ended the third quarter with 5.19 million subscribers paying for Pandora Premium, and its other subscription offering, Pandora Plus, which for $4.99 a month has no ads but doesn’t offer on-demand music choices. As such, the company remains dependent on its ad-supported service for the bulk of its revenue.

“We are only at the very beginning of what can result in a wide range of outcomes for both the subscription as well as the advertising business,” said Credit Suisse analyst Stephen Ju.

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For its third quarter, Pandora reported a loss of 34 cents a share, on $378.6 million in revenue, compared to a loss of 27 cents a share, on sales of $351.9 million in the same period a year ago.

Revenue from advertising made up $275.7 million of the quarter’s sales. While that amount rose by 1 percent from last year’s third quarter, it also fell short of the $289.3 million forecast by Wall Street analysts.

It didn’t help Pandora’s case that the company forecast fourth-quarter revenue in a range of $365 million to $380 million, which missed analysts’ expectations for $412.9 million in revenue.

The report and forecast come after more than a year of upheaval at Pandora, which reached its apex this summer when Sirius XM invested $480 million in Pandora, and co-founder and Chief Executive Tim Westergren left the company. Westergren was replaced by former Sling CEO Roger Lynch, who acknowledged Pandora’s challenges and renewed the emphasis on appealing to advertisers and its ad-based streaming-music listeners.

“It’s clear to me we have a tremendous opportunity to meet the full spectrum of our listeners’ and advertisers’ needs,” Lynch said in discussing Pandora’s results on Thursday. “(We will) reinforce our position as the definitive source for audio advertising.”

Michael Pachter, of Wedbush Securities, said that patience will be needed with Pandora, but that with Lynch in place, the company should do a better job of spelling out to Wall Street where it will put its emphasis in the streaming-music market.

“These guys are now focusing on Pandora’s core business, and are going to try to ramp advertising back to where it had been working for them,” Pachter said.