When the name Jethro Tull is mentioned to anyone born in the second half of the 20th century, a song will come to mind.

It might be “Aqualung.” Or “Living in the Past.” Or “Bungle in the Jungle.” Or “Thick as a Brick.” Or “Locomotive Breath.”

Most likely the image this name summons is the band’s literate frontman, Ian Anderson, playing flute in his unique perched-on-one-bent-leg position, looking much like a deranged flamingo.

Anderson sees his music living on in fans as the biggest lasting tribute to Tull, which will play at 8 p.m. Aug. 23 at Merrill Auditorium at Portland’s City Hall.

“There are certain levels of appreciation that far outshine material industry accolades,” said Anderson recently from his 18th century country home located about 100 miles west of London. “You walk on stage any night, and you see 2,000, 5,000, 10,000 people who bought tickets to come and see you. And that’s the real test. It’s about your work in progress, not a piece of nostalgia, or a piece of kitsch that you hang on the wall.”

As far as who’s in the audiences at a Tull concert these days, Anderson said it’s much the same as when the British group first played in this country in 1969, opening for Blood, Sweat & Tears at the Fillmore East in New York City.

“It’s everyone from teen-agers to those with senior citizen bus passes, although I doubt they’d show them to you,” said Anderson, 54.

Despite their illustrious history, Anderson and his mates, guitarist Martin Barre, drummer Doane Perry, keyboardist Andrew Giddings and bassist Jonathan Noyce, are on the road for eight months this year.

“Beethoven didn’t rest on his laurels; Muddy Waters didn’t rest on his laurels,” he said. “They had a job to do, they got it done, then they died. I feel the same, and am aware of the passage of time. I need to get out the creative urges.”

Anderson refuses to become a nostalgia act, continuing to create new albums, most recently 1999’s “J-Tull.com” and his own “The Secret Language of Birds,” released last year. Tull, named after an 18th century English agricultural pioneer who invented the seed drill, has to gain new fans on the road, since radio doesn’t have a home for them anymore.

“We can’t find a niche,” Anderson lamented. “We’re not classic rock, so it’s hard to get airplay. We have to work much, much harder on marketing and promotion than in the flush of youth. Your biggest competitor isn’t other groups, but your own back catalog. We still sell a substantial amount [of earlier releases] on a worldwide basis, so I’d say we’re gaining a lot of new fans.”

He’s also been asked a handful of times to write music for film, an idea he finds rather distasteful.

“Writing music for someone else’s movie would be a little bit too routine,” he said. “I come from a painterly background, and make music from my own visual reference. Using someone else’s visual reference would be a rather voyeuristic thing to do.”

Anderson remains the only musician to successfully use a flute as a rock ‘n’ roll instrument.

“It’s difficult to integrate into live performance,” he said. “You have to blow really hard to be heard over the other instruments. It’s a frustrating instrument in a lot of ways. If, on my deathbed, a messenger arrives to tell me I’m still the only flute player in rock ‘n’ roll, I wouldn’t be surprised.”

Jethro Tull has yet to be inducted into the Rock and Roll Hall of Fame, something to which Anderson has come to terms.

“I doubt it’s that important for Tull to be inducted into the Hall of Fame,” he said. “That’s about recognition for American pop and rock heroes for the past 40 years. It’s not for us British interlopers. There’s been an isolation of certain British acts deemed too clever for their own good.”

It’s not about the fame for Anderson and Jethro Tull.

“We’re a working band,” he said. “We left school to be professional musicians, not pop stars. It doesn’t have to do with commercial success. It’s a passion. You get up on stage to entertain yourself, and if there’s an audience, so much the better. I’m doing this to make me happy.”

For tickets to Jethro Tull, with special guest Willie Porter, visit the PortTIX box office at 20 Myrtle St., Portland, call 842-0800, or access www.porttix.com.