Stevie Wonder has made a rare appearance at the iHeart ... Then the 42-year-old thanked the singer again, but this time for playing harmonica on her new track Jolene, a cover of Dolly Parton ...

But Stevie Wonder’s career arc is less appreciated ... then drive the Motown hit machine as he learned the ropes. From a happy harmonica-wielding child stealing stage-time from his labelmates ...