i guess to be a great musician you need to born with

accurate hearing, great sensitivity to sounds,passion to music, and creativity. not everybody is born with these.
then even you are born with them you may not be able to get the further training on music. as mentioned in the article you need to learn to read sheet music.you need to learn the history of music.
but great musicians are DEFINITELY geniuses. no doubt.
they cannot be just trained in school.