A trio of Am Law 100 firms are advising on a deal announced Monday that will see Sirius XM Holdings Inc. acquire streaming radio service Pandora Media Inc. The combination, if completed, will create the world’s largest audio entertainment company.

Baker Botts and Simpson Thacher & Bartlett have taken the lead on the proposed deal for Sirius XM, which is seeking to buy the rest of Pandora in an all-stock transaction valued at $3.5 billion. The satellite radio giant had already purchased a 19 percent stake in Pandora last year in a separate $480 million deal. Sirius XM’s interest in investing in Pandora comes as the latter copes with competition from other streaming music services, such as Apple Music LLC and Spotify Technology SA, the latter of which went public earlier this year.