Billboard reports that RCA Records has selected a second single for American Idol 2 runner-up Clay Aiken ... but that the new single, "Invisible," will not be commercially relesed. Instead, like American Idol 1 winner Kelly Clarkson's second single, "Miss Independent," "Invisible" will be issued only in a promotional version for radio stations and other industry recipients.

Clay's first single, "Bridge Over Troubled Water" b/w "This Is the Night", went platinum -- the first single to do so in the period of its release since Elton John's "Candle in the Wind 1997" (dedicated to the late Princess Diana), and so we have to admit to a little surprise at RCA's decision to withhold a second commerical single. Even though Clay's self-titled first album, which also will contain "Invisible," will ship on Oct. 14, we expect that there will be a lot of interest among Clay fans in acquiring the single. Looks like some of them may be spending some time on eBay shortly....

We should point out that at least one other current artist has had a top-selling single -- which was the album's second -- followed closely by a top-selling album. Hilary Duff, whose current single "So Yesterday" spent two weeks at #1 ahead of Clay, now has the top-selling album in the U.S., Metamorphosis, according to Nielsen SoundScan -- while "So Yesterday," the follow-up to her prior hit "Why Not" (which is also on the CD), continues to hold on to a top slot in the singles chart.

On the other hand, considering the success of "Miss Independent," we're willing to give RCA the benefit of the doubt regarding "Invisible."