sustaining pedal vs foot lever

sustaining pedal and foot lever both are nouns.

Word	Noun	Adjective	Verb	Adverb
sustaining pedal	Yes	No	No	No
foot lever	Yes	No	No	No

As nouns, foot lever is a hypernym of sustaining pedal; that is, foot lever is a word with a broader meaning than sustaining pedal:

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

Other hypernyms of sustaining pedal include foot pedal, pedal, treadle.

sustaining pedal (noun)	foot lever (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