If you're even remotely caught up in World Cup fever, you've probably heard K'naan's upbeat anthem "Wavin' Flag." The Somali-Canadian rapper recorded a new version of his 2008 hit just for the global tournament, stripping out references to war and hunger in favor of odes to the unifying power of soccer. But wait -- listen more closely to that five-note vocal chorus that backs the "Celebration Mix" of the song. Does it sound familiar? Coca-Cola (NYSE: KO) probably hopes so.

That soaring choir's actually singing Coca-Cola's signature jingle, a staple of the company's ads for several years now. And while the song makes no explicit references to Coke, the jingle's almost subliminal presence in the song virtually guarantees that somewhere in the back of your mind, you'll be thinking of Coca-Cola.

As well you should; according to Billboard, Coca-Cola has poured almost $1 million in payments and promotional dollars into K'naan and the song, which he rewrote and recorded especially for the soft-drink giant. "Wavin' Flag" is the centerpiece of Coke's $300 million global World Cup campaign, and K'naan is happily riding the song to global stardom.

Since at least 2002, advertisers have actively sought and paid for recording artists to name-drop their products in songs. In 2003, Justin Timberlake wrote and recorded "I'm Lovin' It" for McDonald's (NYSE: MCD); ever since, it has been the fast-food chain's signature slogan. And Gatorade, a division of PepsiCo (NYSE: PEP), recently commissioned producer David Banner and singer Kermit Quinn to create a toe-tapping soul song for the sports drink's "Evolve" campaign.

But the new version of "Wavin' Flag" may be the first example of the next generation of musical product placement. Aside from a thunder of drums, Coke's jingle is the first thing listeners hear, and it recurs in the background throughout the song. It's sneakier -- and admittedly, more brilliant in its sneakiness -- than "I'm Lovin' It" or Banner and Quinn's imaginatively titled "Gatorade Has Evolved." Because the jingle's woven into the fabric of the song, it might more readily bypass an ad-savvy audience's resistance to more conventional marketing.

Given the worldwide success of the "Celebration Mix," that's great news for advertisers -- and yet another reason for wary consumers to keep their ears open for subtle product pitches.

Where, if anywhere, should advertisers and musicians draw the line? Sound off in our comments box below.

Coca-Cola and PepsiCo are Motley Fool Income Investor picks. Coke is also a Motley Fool Inside Value pick and a Motley Fool holding. Motley Fool Options has made a "roll your diagonal call" recommendation on PepsiCo. Try any of our Foolish newsletters free for 30 days.

Fool online editor Nathan Alderman wants to hear "Wavin' Flag" mashed up with Matisyahu's eerily similar World Cup-related "One Day." He holds no financial position in any companies mentioned. The Fool's disclosure policy goes back, and then it goes back, and then it goes back.