In other words, a lot of times such playing sounds like a bunch of unconnected notes, which doesn't make sense musically. Usually the result is not something we all are very proud of or intend to re-create in the future.
But this experience is vital, I would say, not only because it helps to brainstorm all kinds of musical ideas but also because it helps you to understand how much you still have to learn. In a sense, it helps us to feel humble enough at our first steps as improvisors.
Of course, not everything what we improvise in such manner might sound ugly or not worth remembering but if we play something which our brain doesn't orders our fingers, we will have a hard time re-creating the nicely done passages or excerpts that we want to save for the future.
So obviously we have to ask this question - is there a way to ensure that our improvisations become more intentional? In other words, how to let the brain direct our fingers and feet and not the opposite?
Now I can hear some people who are reading this ask that isn't the true improvisation non-rational? Isn't the purpose of improvisation something we create without predetermined thinking and planning?
Of course, improvisation can have many forms and shapes but now I'm talking about this definition of improvisation - Composition at the Time of Performance. It's no different from written down works, the only difference being that when you improvise, you don't have much time to think and correct your mistakes with eraser like you would do when composing on paper with a pencil.
Let's come back to our concept that our mind has to direct the fingers.
I think it's easier to achieve that than we think it is. Although you might be tempted to say that only geniuses can create something on the spot and it would sound like a fully worked out written composition, I think everyone is capable to achieve that on his/her level.
Of course, it wouldn't necessarily be a 4-part scholastic fugue right away but we can reach this level very gradually (remember the concept of "Baby Steps"). Let's start with limiting the possibilities because one of the main problems we face when improvising is the seemingly limitless number of options we could take and limitless number of paths we might follow.
Think of the 6 most important elements of organ music (the are more of course): melody, rhythm, harmony, registration, texture, and form.
Limit your improvisation to just one single option in each category and master it. Choose just one melodic theme, one rhythmical pattern, one meter, one mode, one registration option, one kind of texture, and one kind of form.
Practice in a slow tempo many times until you feel you can safely add one more option to your "bag of tricks".
If you practice improvisation in this manner, you will discover that it's so much easier to create something much more intentionally and you can grow from there.
Try this approach today.
By the way, do you want to learn my special powerful techniques which help me to master any piece of organ music up to 10 times faster? If so, download my video Organ Practice Guide.