It isn't so much "What you say" (or write)... It's the way you say it! Constructive criticism coupled with anything nice you can point out usually works with most performers, artists, composers and song-writers. But be cautioned... there are those that will "go ballistic on you" if it isn't all "sweetness and light." LOL!
IMHO... a really bad review should be shared only with the person who posted the song or work... in private.
I suspect most of you remember the "way it was" when you took that first step. It takes a bit of courage or even bravado to perform... and I am the equivalent of the "Cowardly Lion" when it comes to actually singing in public. That does not keep me from admiring those of you who do perform... and do it with such style and grace.
----Dave Rice