soft pedal vs pedal

soft pedal and pedal both are nouns.

Word	Noun	Adjective	Verb	Adverb
soft pedal	Yes	No	No	No
pedal	Yes	Yes	Yes	No

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

soft pedal: a pedal on a piano that moves the action closer to the strings and so soften the sound
pedal: a lever that is operated with the foot

Other hypernyms of soft pedal include foot lever, foot pedal, treadle.

soft pedal (noun)	pedal (noun)
a pedal on a piano that moves the action closer to the strings and so soften the sound	a lever that is operated with the foot
	a sustained bass note

soft pedal (adjective)	pedal (adjective)
	of or relating to the feet

soft pedal (verb)	pedal (verb)
	operate the pedals on a keyboard instrument
	ride a bicycle