As verbs the difference between amplifying and lengthening
is that amplifying is present participle of lang=en while lengthening is present participle of lang=en.
As a noun lengthening is
a type of sound change when a sound (especially a vowel) lengthens.
lengthening
English
Noun
(
en noun)
(linguistics) a type of sound change when a sound (especially a vowel) lengthens
Verb
(head)