Audiobook publisher Podium Entertainment has been sold to private equity firms Flexpoint Ford and Shamrock Capital by its owner Presidio Investors, for “north of $400 million” according to the WSJ. Music rights company Gold State Music is also named as a minority investor in the purchase.

Podium said that going forward it is working with the nonprofit Ownership Works “to establish a program giving all employees an ownership stake in the company and aligning the team with Podium’s next phase of growth.”

Started in 2013, Podium has built a catalog of more than 15,000 audio titles, many of them from self-published authors. The company focuses on audiobooks and self-published authors—two industry bright spots.