Christopher Guest's new HBO comedy series "Family Tree" starts off from an autobiographical place. Like the show's hero, Tom Chadwick (Chris O'Dowd), Guest once inherited a trunk of family mementos and became obsessed with tracing his own ancestry. Now Guest and co-creator (and Guest repertory player) Jim Piddock have turned that into an ongoing series (it debuts Sunday night at 10:30) that's a mix of Guest's usual absurdity and some more serious, even sweet talk of the meaning of family.

I reviewed the series earlier in the week, and I spoke with Guest about having a sane leading man, the key to telling stories about ridiculous people without being mean, ventriloquism, and more.

This is a bit of a departure for you, in that the main character isn't deluded, but fairly sensible, which is the sort of thing you haven't really done since "The Big Picture." Why did you decide to do that?

It was intended from the beginning that he was going to be kind of an everyman guy that people could relate to in this search, because of the state that he's in at the beginning, when he's lost his girlfriend and his job. We were hoping people would find some attachment. Chris is a very accessible and kind of lovable character guy. He's also funny; he's charming. That was really the guy we wanted to have. I suppose this is different. Typically, it's a bunch of people who are deluded in different ways, and so this is a different model — and it's also different in the sense that he's the lead. In previous things I've done, it's been quite an ensemble of people doing it. But this was the format of the show.

Does it have anything to do with the fact that this is a series as opposed to a 90-minute film? Could you do a TV series with a Corky St. Clair-type character?

Personally? Wow. That, I don't know. I approached each one of these episodes like a small film. But in the sense this is a continuing story. This really couldn't have been a film, with three acts and an ending. There really isn't an ending in this. There may be quite far down the line. So we developed this much longer arc. It's a good question. I didn't really consciously think about that idea, but if one was to after the fact, you can say, well, you want someone that you can kind of latch onto that has some stability, but I don't really know. It wasn't thought about in a conscious way. It's just that we always knew that the character was going to be that kind of person.

A number of the characters he's surrounded by suffer from the sorts of issues you find in other Christopher Guest projects. But how did it change the writing that you and Jim were doing together having this stable, calm center?

It was important firstly because of the emotional line that goes through this. For me, just in general, I like doing things that are supposed to be funny, and hopefully they are to people. But it's equally as important to me to have some emotional basis for these characters. Even if it's Corky, I think — I think — people liked him. Even though he wasn't talented and wasn't the smartest person, there was a part of him that people liked because of  who he was. Without that, then it's a sketch. It's a three-minute sketch and it's a different thing. When you work on something — we're in our second year of working on this — it's a big investment in time. For me, it's more fulfilling to have that as the basis for this character. You want him to be likable and funny, but you also want him to be on this emotional rollercoaster as well. Especially at the beginning. Things change when the characters come to the US; the whole thing brightens up. The surrounding people are still quite eccentric — there's Bob Balaban and Ed Begley and Fred Willard — but Chris's character changes, and there's some hope now in his life.

It's interesting what you said about Corky, because that's always something that's struck me about your work: you tell these stories about very ridiculous people, and yet it's never in a mean-spirited way. You're always able to find something about them that you like. Even "Red, White and Blaine," you can see pieces of that that could be good if more people were involved.

There's no question. As an example, when we wrote that show, the characters are doing the best we could. We didn't want to make it this total piece of shit, because then it's not entertaining or interesting. In the same way with any music we've done, whether with "Spinal Tap" or "A Mighty Wind." It's a trick. You have to write engaging melodies. It's a little off. The lyrics are usually the thing that's off. There are some interior musical jokes. But it has to work on that other level, and you do have to root for the people.

Well, with Nina Conti's character (Bea, the hero's sister, who often speaks through a monkey hand puppet she's had since childhood), on the one hand it's so silly that she's talking through this monkey. But you're also acknowledging that she's a fairly damaged character and Monkey has ruined her life. It's a really interesting balance you were able to strike with her.

Nina is a ridiculously gifted actress, to begin with. What I found for the most part is that people who do ventriloquism, it's a little more one-dimensional, historically. Nina began as an actress, and was a very good actress. What she imparts with this character is that there is a darkness to it. The monkey, though, tells the truth, invariably. The monkey  tells the truth,speaking for her. I think, in looking at this in the long run — if this show ever goes anywhere — it would be interesting to know if that dynamic changes, when she gets some awareness of all this. I love the dark part of it. To me, that's crazy that she gets to be in these situations, that eventually the family are just looking at the puppet as a member of the family — her proxy.

Your character in "Best in Show" goes into ventriloquism at a certain point. How long have you had an interest in this?

When I was on "SNL," I played a Spanish ventriloquist. It's something that when I was a kid, I used to do with puppets. No one taught me how to do it, I just did it. I didn't practice; I just literally did it on the air. I did it in "Best in Show," and after I made "Best in Show," I found a diary from a relative of mine who was born in 1797, and as a child, he wrote that he was the mischief-maker in the family and did voices and sounds and became a ventriloquist. It was really quite chilling to read that. I had no idea prior to making that film, or the other thing. He then became an actor in London in the 1820s and 30s. That's bizarre. Because his description of himself was really the description of me as a child: experimenting with different voices and sounds and things.

That's amazing. How was it working with Jim Piddock as a co-writer. Often, you've written with Eugene Levy on these projects. Was it because you specifically wanted a British voice in this?

Yes. Jim has worked in my films as an actor. Because I decided I wanted to begin this story in England — even though one of my feet is in London, because I lived there back and forth as a child and my dad was English — I wanted to make that whole. Working with Jim was a fantastic thing. We approached it very casually at first, just having a series of lunches. Our sensibility was a perfect match, and we had a fantastic time doing that.

There's a number of your regulars in this, but there are also newcomers like Chris O'Dowd. How was the adjustment for them?

Tom Bennett and Chris were people I met only a year ago in London, and I'd seen Chris's work, and I'd seen a little bit of Tom's work. In any of these situations, it's true for the initial meetings,  there's nothing to read in the conventional sense — there's no dialogue written. It's just a meeting where I talked to them for 20 minutes or half an hour, and I have to make some intuitive decision and say, "I think they can do this." It's a big jump And because there's no dialogue, and there's not even a rehearsal, it's a huge jump. We're on the set, I've discussed this with them, I have a whole back history for them. They know who the characters are; it's not just random stuff spoken about. The scene itself has a structure, a skeleton, a beginning, middle and end. And then we go. I say action, and they start talking.

Was there an adjustment period on the set, or did the two of them take to it quickly?

There's no time for adjustment. If it doesn't work for 10 seconds, it's kind of time to go home. It can be somewhat anxious for people who have never done this, and it's even anxious for people who have. Because it's so black and white, in the sense that this can't just be okay; this has to really work. It has to be real first, and then the funny stuff is the icing. It has to be all organic and real — even though there's a woman with a puppet talking, it has to fit into some reality that the show represents. But again, it's no ramping up to this. It was just really hitting the ground running, and Chris and Tom were just right away, instantaneous relationship. They had never met. They'd met in the dinner before, literally two days before. Hadn't worked together or met, but it looks like they were friends when they were kids.

I remember when "Spinal Tap" came out, so much of the media coverage had to explain the concept of a mockumentary, and that this wasn't a real band and Rob Reiner's name wasn't Marty DiBergi. Close to 30 years later, the form is so well understood that there are all these shows like "The Office" and "Modern Family" that can use the structure with little to no explanation at all. Are you able to take advantage of that increased audience knowledge at this point?

I do what I do. I just do what I do. I chose to do it in this way. I've done it before, so I could've chosen some other way I suppose, but that's what I do. It's very different from those other things you mention, because those are scripted shows. So it is radically different, if you think about that.

Finally, I want to ask about these terrible fictional TV shows that Michael McKean's character spends so much time watching. How did you come up with those, and what did you have to do to make them seem so plausible?

We came up with that early on in the whole thing. We thought it was a great description of those people to show what people watch, as another view into that character. In McKean's sense, it represents an older person's values, in the sense that they're horribly written, and they're also politically incorrect and probably considered sexist now, and that's what he likes. We shot them in the same place those things were actually shot in — those sitcoms in the '70s. We went to the same studio, had the same people who made those sets make them, the whole thing. And it was really fun to write them, and the modern-day ones, equally. They were equally fun to do for different reasons, that it sheds a light on the characters.

Alan Sepinwall may be reached at sepinwall@hitfix.com