Soul music icon Stevie Wonder stunned a young pianist in California over the weekend when he joined him for a rendition of his hit Superstition. The singer heard Grayson Erhard performing the tune in the lobby of the Anaheim Marriott as he arrived for the National Association of Music Merchant's (NAMM) 2017 convention, and when the youngster confessed he didn't know the words to the second verse, Stevie walked up to him and whispered them in his ear.