likes of which mainstream audiences have rarely seen 
(ROOT (SBAR (NP (NP (VBZ likes)) (WHPP (IN of) (WHNP (WDT which)))) (S (NP (JJ mainstream) (NNS audiences)) (VP (VBP have) (ADVP (RB rarely)) (VP (VBN seen))))))
(ROOT (SBAR (NP (NP (VBZ )) (WHPP (IN ) (WHNP (WDT )))) (S (NP (JJ ) (NNS )) (VP (VBP ) (ADVP (RB )) (VP (VBN ))))))