Anyone can learn how to play spontaneous compositions; it’s just a matter of sitting down at the piano and deciding that you’re going to play something completely new. It helps to know some theory so that you can have a basic idea of what you’re doing rather than just hitting random notes.
Know your key signatures, know your chord progressions, one of the best ways to start a spontaneous composition is to play one of your favourite chord progressions and then feel the tune and start playing it.
Let the tune take you where it wants to go, if it sounds like you should go to a new chord progression for the next part of the tune try and work out what would be appropriate on the fly, that’s why you need to know some theory, so that you can make the appropriate choice of chords for the tune and visa versa, the right tune for the chords that you are playing.
But let your imagination take part as well, don’t just go on what should or shouldn’t sound good, if you feel that you want to play something in particular that you know might not sound right, go ahead and do it anyway, remember this is the best thing about it, not knowing what’s going to happen.
Once I recorded one of my own spontaneous compositions and when I heard it back I was amazed at how beautiful it sounded, it seemed to have the most original tune I had ever written, it took me on a journey, everyone I show it to gets taken somewhere when they listen to it.
Try it some time, set up your recorder and then play, when you hear it back you will be thinking, did I play that or then a gain you could be thinking quick turn it off. It will be slow going at first but the more you play the better you’ll get and the more compositions in general that you compose the better you’ll get at spontaneous compositions as well.
The same rules that apply to composing music in the normal way also apply to spontaneous compositions, it’s just that you have to know your stuff so well that you can do it on the fly as you play, if you find that you don’t have the necessary skills and your compositions are not coming out that well, keep composing the normal way and in time you’ll get better and better and wonder how it was that you weren’t able to do it.