loud pedal vs treadle

loud pedal and treadle both are nouns.

Word	Noun	Adjective	Verb	Adverb
loud pedal	Yes	No	No	No
treadle	Yes	No	Yes	No

As nouns, treadle is a hypernym of loud pedal; that is, treadle is a word with a broader meaning than loud pedal:

loud pedal: a pedal on a piano that lifts the dampers from the strings and so allows them to continue vibrating
treadle: a lever that is operated with the foot

Other hypernyms of loud pedal include foot lever, foot pedal, pedal.

loud pedal (noun)	treadle (noun)
a pedal on a piano that lifts the dampers from the strings and so allows them to continue vibrating	a lever that is operated with the foot

loud pedal (verb)	treadle (verb)
	operate (machinery) by a treadle
	tread over