Sure, I think we all talk to ourselves.    And I sing to myself too.   I've done it for years--especially walking to the subway on the way to work.   It was 4 long songs or 5 short songs to the subway.   Doo-wop songs--8 or 9. And when I'd do it--pretty low in volume--other people would cross to the other side of the street. Who is this guy muttering to himself?

But now technology has caught up to me. It's considered completely normal to talk--even an animated conversation--, sing, etc. to yourself on the street--it's assumed you have a Bluetooth or some other device in your ear.