That’s interesting, I myself can sometimes think without a monologue. I did it just now, and I am not sure if I do not use words, but I do not actually hear them, but I know the thoughts are there somehow. It often happens on its own when I have a lot of thoughts at the same time or think really fast about something.

But usually I talk to myself in my head, this is either a monologue or a sort of dialogue, and I often tell myself to shut up out loud when no one is around. I also imagine music, and I can enjoy it this way, and I do so pretty accurately. I play by ear.