I've always wondered about hyperfocus. There seem to be different issues that are hard to define (as always): focus (as in lack of distraction), interest (as in motivation to do something), and the ability to *control* focus and/or interest (executive function?).
My experience in short is: I don't have good focus. I've never been able to concentrate with sounds or visual distractions. I need complete silence and no people can be close. However, I have super intense interests. I can get obsessed about a particular problem or issue and can dedicate every single waking hour to it. I can't tune out things, though. A sound would distracted me. But I would go back. Switching tasks would be very, very difficult.
I don't have much control over it. So going back to your dad, no, I can't magically direct my attention. If I don't care about something, it's very hard to get motivated to do it.
Having said that, though, many times the difficult part is getting started. In school, I wasn't interested in several classes, but once I got started with a task the motivation to do well would keep me going. Many times I would get suck into it because I have a lot of curiosity. It's like with a book that you are dreading to read but once you start reading you realize that you want to continue. And then, you are in hyper-interest mode.
I have read about autistic people who are so focused that you can't even talk to them. Like in a trance. Kind of what
@330 is describing. That's not me for sure. BUT, I can be like that when I daydream. People think I'm gone, which is correct