spectators will indeed sit open-mouthed before the screen , not screaming but yawning . 
(ROOT (S (NP (NNS spectators)) (VP (MD will) (ADVP (RB indeed)) (VP (VB sit) (S (ADJP (JJ open) (HYPH -) (VBN mouthed))) (PP (IN before) (NP (DT the) (NN screen))) (, ,) (S (RB not) (VP (VBG screaming) (CC but) (VP (VBG yawning)))))) (. .)))
(ROOT (S (NP (NNS )) (VP (MD ) (ADVP (RB )) (VP (VB ) (S (ADJP (JJ ) (HYPH ) (VBN ))) (PP (IN ) (NP (DT ) (NN ))) (, ) (S (RB ) (VP (VBG ) (CC ) (VP (VBG )))))) (. )))