more like 90%. If you want some inspiration look up old-ish movies(not newer than early 90s but not older than 70s, the newer ones have tech, the older ones usually trained singers...) with major actors singing a song. These actors will most likely have no proper training(former stage actors and such aside, thats why i said major actors...). but will be given coaching for a short time. Will they pass the judgement of a general audience? some did... And that should tell you a lot. Even with all the short term coaching in the world and being well trained in imitation, they still dont always pass the general audience barrier. Not even to begin of people with any experience with actual singers. For them its as obvious as all the bad instrument playing attempts in movies you will probably have laughed about before. So i conclude that there is probably no way around boring old practice, and a lot of it. Using a recording device is a good tool by the way, but only if you know how to fix the issues you hear (and probably frustrating). thats why i suggest a teacher at least as an initial pointer.