I look at "under-rated" as something very different from being little known. I take it to mean, "known but not fully appreciated." A good example is the late Cisco Houston. For much of his musical career he played second banana as Woody Guthrie's sidekick. You could hear his wonderful tenor harmonies, but you had little sense of him on his own. When Woody got too sick to perform anymore, Cisco finally broke through as a solo artist. That;s when people discovered he had a deep rich voice and a style all his own. But pretty soon Cisco himself got sick and died of cancer just as the folk boom was about to happen. Had he lived, he might have been remembered as one of the great ones. Instead, he is just a footnote to the Guthre legend.