Pandora Media Inc's co-founder Tim Westergren stepped down as chief executive and board member, less than a month after Sirius XM agreed to invest in the music streaming company.

Westergren, who co-founded Pandora (P.N) in 2000, served as CEO and president for about two years until July 2004, before returning to lead the company in March last year.

Since his return, the stock has tumbled 22 per cent. Pandora's shares were down 0.6 per cent at US$8.41 on Tuesday.

Sirius XM Holdings Inc (SIRI.O), controlled by media mogul John Malone's Liberty Media Corp, had said it would invest US$480 million in the company, get three board seats and the right to pick the chairman.

"We expect the new CEO of (Pandora) to come from (Sirius) directly, or from John Malone's extensive rolodex," Needham & Co analyst Laura Martin wrote in a note.

Westergren's departure implies Sirius XM is quickly getting its own people in place at the top of Pandora, she said.

Reuters had previously reported that talks about Sirius XM buying the company outright ended unsuccessfully over price disagreements.

Pandora also said on Tuesday that President Mike Herring and Chief Marketing Officer Nick Bartle were leaving the company.

"It isn't clear whether there are experienced people actually running the company," Wedbush Securities analyst Michael Pachter said.

Pandora named Naveen Chopra, who was hired as chief financial officer in February, as its interim CEO.

The company, which has never turned a profit on an annual basis, faces intensifying competition from services such as Sweden's Spotify, Apple Inc's (AAPL.O) Apple Music and Alphabet's (GOOGL.O) Google Play Music.

In May, Pandora cut its full-year revenue forecast and reported its slowest ever revenue growth and its biggest-ever loss since going public.