softly vs quietly

softly and quietly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
softly	No	No	No	Yes
quietly	No	No	No	Yes

As adverbs, softly and quietly are synonyms defined as:

softly (adverb)	quietly (adverb)
with low volume	with low volume
with little weight or force	with little or no sound
used as a direction in music; to be played relatively softly	with little or no activity or no agitation (`quiet' is a nonstandard variant for `quietly')
in a manner that is pleasing to the senses	in a restful manner