what punk rock music used to be 
(ROOT (SBAR (WHNP (WDT what)) (S (NP (NML (NN punk) (NN rock)) (NN music)) (VP (VBD used) (S (VP (TO to) (VP (VB be))))))))
(ROOT (SBAR (WHNP (WDT )) (S (NP (NML (NN ) (NN )) (NN )) (VP (VBD ) (S (VP (TO ) (VP (VB ))))))))