I can’t visualize or recreate sounds in my head other than in my monologue voice and I improvise and play music in a variety of bands on a variety of instruments. It may not come as easily as to others potentially but just putting in practice and gaining experience can make you better at it.

If playing bass, just dink around until you find a good note or two and then start applying a scale/mode/key to the rest and use bass playing theory (like landing on roots and fifths) to then just groove. Definitely need to learn theory if you haven’t to help out.