ASPEN — I'm not a doctor; I don't even play one in newsprint. But after just one session, by phone no less, even I can confidently diagnose Dave Hill with a case of multiple personalities.

Dave Hill Explosion, the show he has been presenting for a year and a half, opens with Hill in his explosive mode. Hill does his song-and-dance theme number, shows the short videos he makes specially for each performance, gets semi-naked, and generally exhausts himself with activity.

"I read and sing and dance and jump around like an idiot,"' said Hill, speaking from his home in New York City's West Village. The theme song, he continued, is "physically demanding. At least for me, because I'm not in that great a shape. It's a lot of lunging and gyrating. I'm a little worried about doing that in the altitude; worried about getting worn out. Because I get pretty worn out doing it here."

"Then I have a guest on."

To hear the Cleveland native describe it, the transition from comic crazy man to genteel, Merv Griffin-like conversationalist is a jarring one. But he assures there is a smooth flow to the Explosion; the first half serves, perhaps, as a means for Hill to relieve himself of his nervous energy.

"By the time the guest comes out, I've jumped all over the place, took my shirt off," Hill said. "I'm physically exhausted. By the time the guest comes out, I'm not nervous anymore."

Hill, the interviewer, sounds like the mellow, thoughtful alter-ego to Hill the entertainer. He says he is genuinely interested in finding out about his guests while they are onstage with him. The object is never to make sport of them, and certainly not to drag them into the manic energy that has been left behind in the first half of the Explosion.

"It's never to make fun of them. I try never to do that with my performing," said Hill, who writes a song for and about each guest, and performs it in the show.

"That's the easiest route to go, to make fun of people. If anything, I'm the idiot on my show. I'm not the nicest guy in the world, but I don't make fun. It's to have fun. And it's fun for me, because a lot of the times the guests are people I'm a fan of."

Hill stays away from comedians as guests, "because I'm a comedy person, and it wouldn't be strange for me to be speaking to another comedy person," he said. His guests do end to come from the arts and entertainment worlds, and most of them with a bit of braininess to them: singer Rufus Wainwright, musician Moby, writer Malcolm Gladwell and Randy Cohen, who writes the "Ethicist" column for The New York Times Magazine. Other guests have included Victoria's Secret model Frederique van der Wal and Kitten Natividad, a stripper and frequent actor in the softcore films of Russ Meyer.

Hill performs his Explosion twice at the U.S. Comedy Arts Festival: at 10:30 Thursday and at 11 p.m. Saturday, both at the Tent. His guest tonight will be Snowmass Village resident Judith Light, best known for the sitcom "Who's the Boss?" and who is featured in the romantic comedy "Ira & Abby," being screened in the USCAF's Film Program. On Saturday, Aspen Mayor Helen Klanderud will be Hill's guest.

Hill says that, unlike on most TV talk shows, his guests rarely have a current project to pitch, so his interviews tend to be more wide-ranging and unpredictable. He rarely conducts pre-interviews, partly because he doesn't have the time and partly because doing so would take away from the spontaneity.

"I end up learning a lot about a person," said Hill, who has done his explosion at a variety of New York City venues, including the Upright Citizens Brigade Theatre, and at the Upright Citizens Brigade Theatre in Los Angeles. "At least as much as I can learn from the Internet."

Sometimes what he learns is his guest can be more volatile and confrontational than Hill himself. Sandra Bernhard and Moby are two he picks out as having sparked a tiff with the audience.

"Which is not to say people pelted them with garbage," Hill said. "But they came out and were unruly. That certainly makes for a memorable night. That's my favorite, when a guest comes and goes nuts, and I don't know what's going to happen.

Hill, who had been a newspaper journalist and rock musician, began his comedy career some two-and-a-half years ago. He was instantly drawn to the more experimental side, doing readings, showing videos, or just talking about something of interest. Executives with the USCAF asked him to come up with a showcase for last year's festival. He ended up not appearing in Aspen but took the opportunity to examine his diverse set of talents and personalities.

"It forced me to sit down and figure out how all this stuff fit together and related to each other," Hill said. "So I put together a show, this is me, for 40 minutes."

Reflecting on what sort of performer he wanted to be, Hill flashed back to his early admiration for late-night talk show hosts.

"My fantasy would be to take over for Letterman," said Hill, who recently sold his screenplay, "Now In Paperback," in which he plays a publicist on a book tour. "Growing up, my friends and I all used to watch his show, and we all thought he was doing it just for us.

"I didn't think of those guys as comedians, but just funny guys, guys who were entertaining and looked like they were fun to hang out with. Guys who were just out in the world and acting like idiots all the time. That appeals to me. What I like about my job is I get to act like an idiot. I get to do what my friends and I did when we were 15, sitting in the basement and entertaining ourselves. And so far it's going OK."

<b>Other shows</b>

Other live events today in the USCAF include:

• The storytelling program The Moth: "The Show Must Go On" (4 p.m., Belly Up).

• Alan Zweibel's "The History of Me" (5 p.m., St. Regis Aspen ballroom).

• "The Rickles Project," a screening of director John Landis' film on comedian Don Rickles, followed by a Q&A with Rickles and Landis (7:30 p.m., Wheeler Opera House)

• An Evening with Steven Wright (10 p.m., Wheeler).

Stewart Oksenhorn's e-mail address is stewart@aspentimes.com