How Do You Develop Your Musical Themes?

What are the techniques of developing musical themes? Which ones do you use in your compositions?

Look at what Bach did: transposition, invertion, retrograde, diminution, etc.

Put it in a fugal passage, change the texture, change the instrument if possible.

Beethoven is really the master of development so look at scores to see what he did to his initial motives.

I my music I am frequently trying to present simplicity and complexity of musical material: simple melodic lines, clear rhythms, triads or other simple harmonic contructions vs aleatoric counterpoint, complex rhythms, dense harmonies, including clusters.

These are nothing more than material which I use in my composition. I also try to put in youthful energy and passionate love for my creativity. Therefore I never write music purely with my brains even though most of my ideas are purely abstract and rarely follow a specific subject.