. I dont assume everyone can, but i do believe that it is a majority rather than a minority that can reach a reasonable degree of competence if they work at it and have a good teacher
well this is where guidance can come in, some people might be ok at one aspect of songs perhaps shanties, years ago in folk clubs this might happen. they were helped and steered in a certain direction[ i do not mean the door]although i have met a very very small amount of totally unmusical people
people were helped and guided towards what they might be able to manage. but i think you have to be positive and positive about people