You know why I believe in this so much? I'll tell you why.
I joined the school band when I was in fifth grade. I played trumpet. I didn't particularly like playing the trumpet and I only mildly enjoyed class. When, in high school, we had to learn music theory, I was almost completely mystified by things like the Circle of Fifths, chords and other musical concepts. I never did particularly well and and mostly languished in the beginner level classes while my classmates moved on to the advanced ones.
I never showed any real musical talent; indeed, folks around me probably thought I didn't enjoy music at all. I didn't listen to popular bands like other kids my age listened to and I was very vocal about my disappointment in the music on the radio. I appeared to be a pretty un-musical young person.
You know what though? Now I play piano and the banjo. I've learned and understand a great deal about music theory. I've made several hours worth of music. I went to school for Audio Engineering and got an A- on my final independent study (writing and producing a six-song album.) Someone thought my music was good enough to ask me to write music for their game. I write about music, for a site you may have heard of, and actually have people writing to me, me for answers about making music. This is the guy who could barely stay afloat in band class! If those poor folks only knew!
Am I writing just to praise myself? Well, after putting all that together I have to admit it does sound pretty awesome, but that wasn't my point. My point is that if I could do all that without any 'inborn' musical ability, then anyone else can do it too. I don't see myself as a particularly self-motivated guy either, so I'm sure anyone out there can probably do better than me.
I've heard many people say that they won't pick up an instrument simply because they think it is too late for them to learn. There are a lot of scientific studies that say people can't learn as effectively past their teenage years and after age 17 your neural pathways are pretty much do-blah blah blah. Forget that crap. Maybe my neural pathways aren't as flexible as they once were, but I have many other skills and traits that come with age that make up for that problem, like self-discipline, good time management, big-picture thinking, and the prospect of getting paid for what I do. I had none of these things when I was a kid, and my learning was probably much slower because of it.
The only reason you might think that you are aren't a musical person is because society tells you that you aren't. But the fact that you can enjoy music scientifically proves that you can also make it, since you use much of the same parts of your brain for both listening and performing. In many hunter-gatherer cultures, the concept of musical talent doesn't even exist. Everyone is taught how to make music and dance from a young age. This is how our own cultures were until relatively recent times. Why the change? Different values? Elitism? Who knows? You shouldn't let it hold you back.
So what are you waiting for? Angels to come fluttering down, bestowing upon you a golden guitar? You definitely have no excuse now. If you do still have an excuse of some sort, you can bet that the Makeshift Musician will do it's best to unceremoniously blast that one out of the water too. Go pick up an instrument and start playing!