Even if you don't know anything about music, you can be a musician immediately --- really!
There is a very common idea out there that says that only people with special gifts can make music, and that only extremely rare folks have that added mystical ability to compose and improvise music that has never been done before.
Well, there is a certain measure of truth in that, as there is about giftedness in all areas --- but I disagree with the word "only"! Music has a structure that will do all sorts of things for you if you just let it. And the simplest introduction to this is something I still enjoy after a lifetime of improvising:
Look at a piano keyboard. You'll see that the black keys are arranged in a repeating pattern of twos and threes. If you play all the twos you'll see that they're all the same two notes, just different by being in higher and lower octaves. The same is true of the threes, too. Well, combine a set of twos with a neighboring set of threes, and you'll get a nice-sounding combination of five notes that happens to be the most universally popular scale of all time --- a "pentatonic" (five-note) scale. (Some very famous tunes use that very scale, such as "Amazing Grace.")
Now you have the structure of music at your disposal, and you can make nice music without knowing anything else!
Pick three or four notes (technically we call this a "motif"), say, the bottom of the group of three keys and then the two of the two-key group. Play those three notes twice in a row, then repeat them in the opposite order, then back to the first, then add one of the other notes you hadn't played yet, or change one of the notes, and just start wandering around on the black keys and occasionally returning to the first set of notes you played. You will probably start hearing a new free-form melody emerging! It may even seem surprisingly organized, and very likely quite pretty.
Keep experimenting: Try a new set of notes, or a new rhythm, a new speed, whatever you feel like. Maybe two different notes at the same time.
I'm aware, too, that some people are expert musicians who have, say, played wonderful Chopin on the piano all their lives but have never tried a single note that's not from a master's written page. This concept is just as freeing for them as for novices!
And now for one last idea: Can you, even at this stage of new improvising, make music that says something special, that creates a certain mood, that moves your very own soul?
I do think so!