A year ago, Pandora Media was full of ambition.

The internet radio pioneer would operate a ticketing company and integrate concert listings with its music streams. It developed an on-demand subscription service to go head-to-head with Spotify and Apple, and had plans to expand internationally. To lead the charge, the company brought back Tim Westergren, its charismatic co-founder, as chief executive.

But on Tuesday, Mr. Westergren left the company after only 15 months at the helm, and over the last few weeks many of the company’s boldest plans have been jettisoned or cast into doubt.

To raise needed cash, Pandora unloaded Ticketfly, its ticketing service, at a significant loss, and accepted a $480 million investment from Sirius XM, giving that company a 19 percent stake and three board seats, including the chairmanship.

Roger Faxon, a Pandora board member, said in a statement that the recent moves were meant to “refocus and reinforce” the company, and that Pandora was still committed to its new subscription platforms.