– Just one day after speculation emerged that satellite radio leader Sirius XM was considering investing in, as opposed to outright buying Pandora, the two companies said Friday that Sirius will buy 19 percent of the Oakland, Calif.-based internet radio pioneer for $480 million.

With the purchase, Sirius becomes Pandora’s largest shareholder, which means it will have a big influence on where Pandora chief executive and co-founder Tim Westergren takes the company.

As part of the investment, Sirius will get three new seats on Pandora’s board of directors. One of those Sirius officials will become chairman of Pandora’s board. The Sirius appointments will expand Pandora’s board to nine directors.

Stan Meyers, an analyst who covers Pandora for Piper Jaffray, said that while Sirius’ investment in Pandora did not work out to the full acquisition that many had expected, “it does meaningfully strengthen Pandora’s balance sheet, which has been weighing in on the stock and delivers a strategic partner that can help grow Pandora in the car.”

“This is a very significant juncture in Pandora’s journey,” Westergren said in a statement announcing Sirius’ investment. Westergren added that Sirius’ involvement with Pandora “gives us the flexibility we need to attack what is becoming a larger and larger opportunity as digital music enters a new golden age.”

That opportunity lies largely in on-demand music streaming. In March, Pandora introduced Pandora Premium, its first fully on-demand subscription streaming option, which costs subscribers $9.99 a month. When Pandora reported its first-quarter results in May, the company said it had signed up 500,000 Premium subscribers on a trial basis.

Pandora also offers Pandora Plus, an ad-free music-streaming option for $4.99 a month that lets users skip an unlimited number of songs and replay songs, as well as its longtime ad-supported free music listening service.

Along with bringing Sirius on board, Pandora is getting out of its business with Ticketfly.

Pandora said it had reached a deal to sell its Ticketfly concert-ticketing business to Eventbrite in a deal valued at $200 million.