(FORTUNE Magazine) – Is Oprah doing for music what she did for books? The publishing world heaved a sigh of relief when Oprah kicked her book club back into high gear last year, since her selections quickly become bestsellers. Now Billboard reports four weeks in a row of huge sales lifts for artists featured on Oprah's stage.

After Luther Vandross made an early-May appearance (his first since a devastating stroke last year), sales of "Song for My Father" tripled, and the tune rose from 118 to 46 on the Billboard chart. The following week Wynonna Judd (appearing with her mother and sister) talked weight issues with Oprah and performed a single song. Judd's last album, absent from the charts since October 2003, reentered at 46 (granted it's not No. 1, but Judd wasn't complaining). After Lionel Ritchie was on the show, his new album moved from 105 to 47, its highest spot since its release two weeks earlier, and his greatest-hits collection made the charts again after slipping off last September. Finally, at the end of May, George Michael used Oprah's show to stage his comeback. His album, which hit the charts at 29, has leaped to No. 12 --his highest ranking since 1999.

Geoff Mayfield, director of charts for Billboard, says the phenomenon isn't new--he saw the Oprah effect in action as long ago as 1990, when Yanni was the beneficiary. And he says artists like Rod Stewart and Michael Bolton have seen rankings spikes from airings--and reruns--of their appearances. But, says Mayfield, "I don't remember an instance where there were four consecutive weeks of this big a spike."

So, Oprah, what about a music club? Alas, a spokesperson for Harpo says that the diva of daytime has never considered it. --Kate Bonamici