They can change the tone of people's voice yes.
( They ( ( can ( ( change ( ( the tone ) ( of ( ( people 's ) voice ) ) ) ) yes ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (MD can) (VP (VB change) (NP (NP (DT the) (NN tone)) (PP (IN of) (NP (NP (NNS people) (POS 's)) (NN voice)))) (NP (RB yes)))) (. .)))
They are able to alter the tone of voice.
( They ( ( are ( able ( to ( alter ( ( the tone ) ( of voice ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP are) (ADJP (JJ able) (S (VP (TO to) (VP (VB alter) (NP (NP (DT the) (NN tone)) (PP (IN of) (NP (NN voice))))))))) (. .)))