By Dan Craft

Don't look back, Boston once cautioned.

A new day is breakin'.

The sun is shinin'.

The road is callin'.

This year, though, the warning has been temporarily suspended as the guitar-loving band embraces its inner anniversary.

No. 40, in fact.

To invoke yet another Boston anthem: It's been such a long time.

For guitarist Gary Pihl, the milestone is especially worth looking back on since it coincides with another ... the veteran rocker's four-decade-long marriage to his high school sweetheart.

That's a number rarely, if ever, attained within his profession, either musically or domestically, he readily admits.

"It is very, highly unusual," adds the native Illinoisan, who was born and reared in Chicago, then transplanted to San Francisco for his teen and young adult life.

Pihl (pronounced "peel") is the second longest-running Bostonian, having joined the band near the end of 1985, and made his transition at one of the pivotal events in Central Illinois rock annals (more about which shortly).

"We are thrilled to be on our 40th anniversary tour," he says of the year-long trek making a stop Tuesday night at the U.S. Cellular Coliseum in Bloomington (preceded on stage by openers Jefferson Starship).

"When I first started playing with the band, I was hoping their 15 minutes of fame weren't up, and that people still wanted to hear the songs from that first album," he says.

And that was 31 years ago, after the band had produced a notoriously slender total of two albums in nearly a decade (1976's "Boston, 1978's "Don't Look Back"), with a third (1986's "Third Stage") in its finishing stages.

"It's a testament to Tom (Scholz)'s genius that the people did, and still do, want to hear the songs."

When last the band passed our way -- a Coliseum show in the summer of '08 -- the band was in a particularly sensitive transition time: recovering from the untimely death of lead signer Brad Delp, who'd taken his own life the year before, and breaking in a new lead singer (Tommy DeCarlo) who had been accidentally discovered online (see accompanying story).

On that tour we witnessed here, DeCarlo was still being joined by veteran rock singer Michael Sweet, who had some down time from his regular gig with Stryper to join that tour and mentor DeCarlo in the ways of rock band stardom and vocalizing.

"It was so nice of him to help out through the transition period because we had no idea then if Tommy was going to work out since he'd never toured with a band before," Pihl recalls.

"As it happened, those two guys really hit it off and became close friends. Tommy learned a lot from those shows, especially in terms of becoming comfortable on stage and knowing how to give it your all."

Indeed: Eight years later, he's still at the forefront of Boston's vocals, with no end in sight. "He's not afraid to take chances now, and the people really seem to love him."

That, says Pihl, will be the main change we'll see from the earlier concert.

From his own perspective as a 31-year Boston member, "looking back now, I see that I've been the luckiest guy in the world, going from one band to the next without even having a day off."

He's referring to his prior eight-year stint with Sammy Hagar's band, which he'd joined in 1977, and which came to a close 45 miles to the east of Bloomington-Normal at 1985's legendary first Farm Aid concert in the University of Illinois' Memorial Stadium.

"Sammy told us that he'd gotten an offer he couldn't refuse: to take over as lead singer for Van Halen," Pihl recalls. "As a result, he said he was going to have to break up the band."

Then Pihl got an offer HE couldn't refuse.

Because the Hagar band and Boston had toured together during the late '70s, Pihl forged what has proved to be a lifelong friendship with Boston's Scholz, who invited Pihl to Boston (the city and the band) to "come and help out" on one last song needing work for the band's long-awaited third album, "Third Stage" (home of Boston's lone No. 1 hit, "Amanda").

"I said sure," Pihl continues. "In fact, I would have crawled on my hands and knees to do that."

He departed the Farm Aid stage, drove to the airport in Urbana and hopped a plane that very night to Boston.

"All he was offering at the time was to play on that one song ... and he (Scholz) pulled out his guitar and said, 'here's the way it goes, and pretty soon we're jamming and playing."

Six weeks later, the song's drum tracks were laid down ... Pihl's introduction to what he describes, with a chuckle, as Scholz's "glacial" production process, during which albums can take years to perfect to his legendarily exacting standards.

"For me, that was the opposite of what I'd experienced with Sammy, where it was always 'what you see is what you get,' with everything off-the-cuff, spur-of -the-moment and by-the-seat-of-your-pants," Pihl recalls.

"In the time it would take Tom to record a single song, Sammy would record an entire album."

He adds: "It's just different approaches ... apples and oranges ... and I've loved working with both."