I "soft talked" several birds last year, low volume and virtually constant calling!
Years ago I had two toms coming across a large field, if I stopped calling they lost interest, I was about out of breath when I finally killed one, I think of that hunt often when calling those birds that are slow to come in.
Like anything it works when it works!
A good friend who I guide with and who also builds all my mouth calls calls really softly volume wise, I noticed this when we were playing with calls in his shop years ago and added it to the arsenal, he is a killer!
I may be stubborn but I ain't stupid...haha