a certain sense of experimentation and improvisation 
(ROOT (NP (NP (DT a) (JJ certain) (NN sense)) (PP (IN of) (NP (NN experimentation) (CC and) (NN improvisation)))))
(ROOT (NP (NP (DT ) (JJ ) (NN )) (PP (IN ) (NP (NN ) (CC ) (NN )))))