Jazz piano preludes. In March I finished a cycle of 24 preludes, all completely written, but most of them are improvisable. Others are really very written out and sometimes very long. It would be difficult, but not impossible, to improvise on them. I'll certainly play a few, but for me the great pleasure of a solo piano concert is not to prepare the program too much in advance, and to let the concert develop organically, to really play whatever comes to mind.
True freedom comes from great discipline.
You have to know your instrument, through physical work but simultaneously mental and spiritual work, otherwise technique doesn't mean anything. Some people manage to make very beautiful music without much technique, but those who are really going into the future have mastered their instruments and bring something new. Consciously or not, they are thinking about the use of traditions to make a new synthesis. Creative freedom only comes after a lot of work. Jimi Hendrix, who never took guitar or harmony lessons, worked enormously on his instrument.