Liberty Media (FWONA) will now be calling the shots at Sirius XM Radio (SIRI -0.85%).

John Malone's eclectic media empire now has majority control of the satellite radio provider. In an SEC filing last night, Liberty Media revealed that it acquired another 50 million shares of Sirius XM at an average price of $3.156 on Tuesday. The move pushes its effective ownership stake from 49.8% to roughly 50.5%.

There's no surprise here. Liberty Media -- acquiring a 40% preferred share stake in Sirius XM when it was cheap and desperate four years ago -- has been nibbling away since March of last year to build its position in the growing radio platform. All it was waiting on was for the FCC to nod in approval, and that happened earlier this month.

Liberty's been making big moves these days. Last week it spun off its premium movie service provider Starz (STRZA) to stakeholders, and the prevailing thesis is that it will now do the same with Sirius XM by taking advantage of a tax-advantaged trust to complete the transaction.

Now, fears of investors dumping a spinoff or the reality that Liberty Media won't be moving the market higher by making open market purchases on Sirius XM shares would seem to pressure the stock, but that certainly hasn't happened. Sirius XM is trading near the four-year highs it set just last week. Sirius XM's board has calmed fears by authorizing a whopping $2 billion share buyback that can now be used to offset any potential selling pressure.

Some investors may be holding out for an outright purchase of Sirius XM by Liberty Media, but that won't come cheap. Even with Starz sending back approximately $1.8 billion in cash to Liberty Media as part of last week's spinoff, Liberty Media isn't made of money.

It will be interesting to see what Sirius XM shares do now that the drama has subsided. The media giant has never been in better shape. Sirius XM is consistently profitable, oozing free cash flow, and closed out 2012 by tacking on 2 million more net subscribers.

Sirius XM owns the premium radio market, regardless of who actually owns Sirius XM.