Hi,
As i say, there are some people who are (without any doubt whatsoever) born to be musicians. And many of these have zero formal training at all (like The Beatles, Jimi Hendrix, Charlie Parker, Chet Baker, etc etc). But HOW MANY OF THEM COME ALONG IN A LIFE TIME !! ??
The rest of us have to learn from and try to adopt the mindset and intillectual level of these musical giants. And we do this thru COPYING (whether that be singing along to, playing an instrument in unison with, transcribing note for note, or whatever). And by doing this (REPETITION) teaches us DISCIPLINE !! Music is an art-form and like all art-forms it requires DISCIPLINE. And the required amount of discipline can be attained via the afforementioned 3 x methods of ‘copying’).
So, to be a little fairer and less black&white about the matter, YES it is possible to gain all these skills without going to music college or having a tutor. However, you will be limited to your choice of instrument for sure. For instance, i am quite certain that it would be near impossible to learn an instrument (to even a very elementary level) such as the Church Organ, Sitar, or French Horn without formal study.
(btw - i am talking about learning the skills to be able to play/improvise/read/compose etc on a physical musical instrument here and not ‘computer generated music’).
Ta,
Paul