a poem of art , music and metaphor 
(ROOT (NP (NP (DT a) (NN poem)) (PP (IN of) (NP (NN art) (, ,) (NN music) (CC and) (NN metaphor)))))
(ROOT (NP (NP (DT ) (NN )) (PP (IN ) (NP (NN ) (, ) (NN ) (CC ) (NN )))))