I think, strictly speaking, both audio and visual versions of songs are supposed to pay royalties. There seems to be a lot of gray area these days, though, with all the online song hosting sites.
Live performances, in which a singer simply gets up and sings (or a band performs at a club or resort)--all royalty fees are covered by the annual licensing fee the
venue (not the artist) pays to one or more of the licensing agencies (like ASCAP, BMI, Harry Fox). I would think a video of an artist singing to the camera would fit this type of performance, as well.
It's the "dramatization" of a song that requires a synch license. I think this includes songs being (more or less) acted out while being sung, as well as background music when something else is happening on the screen. Or stage.
As far as songs being played on the radio, the stations also need to have agreements with the licensing agencies. Because they're playing for the public, they can't rely on the 9.1 cents (per song, per pressing) the recording artist paid to make the CD legal. Restaurants and stores with piped in music also need to pay licensing fees. Depending on where they get their music, it might be included with the fee they pay--like, if they use Pandora for businesses, I think the licensing fee is built into the rate.
That's what I (think I) know.
And, of course, this all applies only to the USA.
Vicki