Here are the companies that could buy Pandora, and why

Pandora is readying the launch of an on-demand music service to compete with the like of Spotify, and is currently trying to lock down deals with the major music labels.

But if the company can't get those deals done, or if the new service is a flop, there will be big pressure on Pandora to sell itself.

Indeed, there was already pressure earlier this year from Pandora's activist shareholder, Corvex, for Pandora to consider a sale, and Liberty Media's CEO reportedly made an informal offer.

In a note on Monday, SunTrust analysts led by Robert S. Peck explored who the potential buyers for Pandora would be. Here's what they came up with:

• Liberty Media/SiriusXM: "Liberty's CEO (LMCA, $22.74, NR) has been reported by CNBC to have acknowledged the benefits of a P/Sirius merger and was reported by the Wall Street Journal to have made an informal $15 offer for P. Liberty Media is 65% owner of Sirius XM (SIRI, $4.10, NR). Further, P's activist shareholder has publicly endorsed a tie-up between P and Liberty/SiriusXM."
• Spotify: "A potential merger of Spotify and Pandora has also been discussed in the press, including Forbes. We believe synergies would be substantial as it relates to product development, marketing, salesforce, content delivery, royalty tracking/reporting, back office, demographics, data, local, in-auto, upsell, and programmatic. A reverse merger could provide Spotify an alternative to an IPO and a liquidity event for its investors."
• Others: "The suitors that make most sense to us are mobile-first and acquisitive with an ad business and amenable to an inside plus feet-on-the-street salesforce model. We believe this includes Verizon (VZ, $51.82, NR) and to a lesser extent AT&T (T, $39.71, NR)."

As to a potential valuation for Pandora, SunTrust uses the $15 per share offer from Liberty Media as a benchmark, but notes that Pandora's senior leadership is financially incentivized to push shares over $20.