( ( Pedal harps ) ( ( use ( ( ( the ( mechanical action ) ) ( of pedals ) ) ( to ( change ( ( the pitches ) ( of ( the strings ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Pedal) (NNS harps)) (VP (VBP use) (S (NP (NP (DT the) (JJ mechanical) (NN action)) (PP (IN of) (NP (NNS pedals)))) (VP (TO to) (VP (VB change) (NP (NP (DT the) (NNS pitches)) (PP (IN of) (NP (DT the) (NNS strings)))))))) (. .)))
Pedal harps use the mechanical action of pedals to change the pitches of the strings.
(ROOT (S (NP (DT A) (NN person)) (VP (VBZ uses) (NP (JJ mechanical) (NN energy) (S (VP (TO to) (VP (VB pedal) (NP (DT a) (NN bicycle))))))) (. .)))