After Google's purchase in January of dMarc, a radio ad broker that holds online auctions of remaindered radio ad space, allowing customers to insert their ads directly into radio play through an online digital interface, the company's partnership with Clear Channel almost certainly represents an elaboration of its "old media" strategy.

The Google partnership will allow Clear Channel's local radio station Web site visitors--almost 7 million a month, according to Clear Channel--to search the Web through Google's search interface, while permitting Clear Channel's local advertisers to expand their presence from radio to online.

Google's stated intention in purchasing dMarc was to allow smaller advertisers who use Google's AdWords and AdSense programs to extend their advertising reach to radio. Google may be using Clear Channel's local station Web sites as an arena for experimentation as it tries to come up with a formula for combining radio and online ad business models.

Looking ahead, Clear Channel has also been a leading advocate of HD terrestrial digital radio, which delivers CD-quality sound and allows multicasts of different program streams on a single frequency, with Clear Channel CFO Randall Mays saying in a recent interview that his company's extensive digital infrastructure makes it uniquely well-positioned to roll out digital multicasts. To promote the digital multicasts, Clear Channel has also been streaming live radio over its Web sites, signaling a further convergence of radio and online media and with it an expansion of Google's potential scope of radio operations.

Meanwhile, in January, Chad Steelberg, CEO of dMarc, referred to HD iBiquity, the company that controls HD radio technology, as a "long-term partner," and in February Bob Struble, CEO of HD iBiquity, mused that digital radio may provide the key to making the Google-dMarc pairing profitable.

This news story is important. I recommend that everyone read it.