an occasionally interesting but mostly repetitive 
(ROOT (NP (DT an) (ADJP (ADJP (RB occasionally) (JJ interesting)) (CC but) (ADJP (RB mostly) (JJ repetitive)))))
(ROOT (NP (DT ) (ADJP (ADJP (RB ) (JJ )) (CC ) (ADJP (RB ) (JJ )))))