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