Clear Channel plans to announce today (April 7) that it will become the first radio chain to feature iTunes tagging across 345 stations broadcasting in HD. The feature allows listeners to press a button on their HD radio to tag a song, store the information in an Apple iPod, then purchase and download songs via Apple iTunes when the iPod is synched with a computer. Polk Audio’s I-Sonic Entertainment System 2, which just hit Apple stores, is the first HD receiver to include the new feature. Other receivers are scheduled to hit retail shelves in the coming months. As the radio industry ramps up efforts to promote HD, it looks to new, interactive features like iTunes tagging to encourage consumer adoption.