Keeping a spark onstage and off

Tim McGraw has discovered the secret to a happy marriage: become a country music superstar before you tie the knot.

"I think it was helpful that we had a lot of success before we got married," McGraw says of the early achievements he and wife Faith Hill notched before saying "I do" in 1996.

"You've got to be pretty self-absorbed early on in order to succeed, I think, not necessarily in a bad way, but you've got to put everything into it, and I think that's hard on a marriage in general," says McGraw on the phone from the couple's Nashville home. "If you had had two artists who were struggling to make it, I think it would be twice as hard."

What's remarkable about the McGraw-Hill union -- the pair come to the TD Banknorth Garden tomorrow and Friday with the third edition of their record-breaking "Soul2Soul" tour -- is the success the couple has been able to maintain separately in an industry notable for lopsided partnerships (see: Waylon Jennings and Jessi Colter, or Whitney Houston and Bobby Brown).

Indeed, they have had eerily parallel careers. Both 40 this year (Hill heads over the hill in September, while McGraw made the leap in May) and natives of the Deep South -- she's from Mississippi, he's from Louisiana -- each found their way to Nashville after dropping out of college. The pretty blonde and the athletic brunet both broke through in 1994. Each has been blessed with No. 1 hits and armloads of trophies and has sold roughly 30 million albums. While McGraw may have the edge in number of albums released -- nine to his wife's seven -- Hill did have their three children, after all.

After 11 years of marriage, the couple has also maintain ed a spark that is as visible offstage as it is on.

In a series of duets, the pair seem to share a secret wink between them. In interviews and television appearances, they are playful, affectionate, and serious about their lives together. Hill calls her husband "an awesome entertainer" and McGraw his wife "flat out one of the best singers in the world."

And, says McGraw, you are as likely to witness that dynamic under the spotlights as you are the fluorescent bulbs of the grocery store.

"I think it's actually a lot the same," he says. "We sort of live in our own world when we're together, especially when we're with our kids. We don't like to be separated, and I think that carries over to the stage with Faith and I, we create this little atmosphere together."

Songwriter Brett Warren, who with his brother Brad has written with McGraw and for Hill and toured with the couple, says that chemistry is a reality, not a glittering fairy tale. "People say it's all a facade that they love each other," he says , with a laugh , of the tabloid press the couple attracts. "Man, they have three children, they've been married for 11 years, they fight just like everybody else fights, they love each other just like everybody else does. They don't breathe different oxygen."

"They are so different as artists," says Brad Warren. "But I think they push each other. It's like a healthy competition, but they support each other."

The couple is also famous for their support of other artists.

"They don't just give credit at some awards show to songwriters," says Brad, "they bring them on tour with them, they bring their careers along."

In addition to the Warren brothers, Hill and McGraw were early champions of Holliston native Jo Dee Messina, maverick duo Big and Rich, and, currently, Stoughton singer-songwriter Lori McKenna, who opens for the pair at the Garden.

"Not only are they the best at what they do, they're good people," says McKenna, who was bowled over by the assistance she's been given by the couple's road crew. She has also witnessed firsthand McGraw's penchant for pranks and Hill's mischievous sense of humor. To which, for the record, McKenna attributes Hill's display of mock outrage at the CMA awards last fall, when she lost to Carrie Underwood. Some viewers were convinced that Hill allowed her inner diva to rear its head. Not so, says McKenna, who was at the ceremony. "Oh yeah, no question [she was kidding]. I don't think she's as easy to figure out as people think she is. People think when you're that beautiful and you can sing that well or you're that famous that you're kind of one-dimensional, and she certainly is not."

"They're crazy loyal," says Brad Warren. "They don't drop people off, they just keep picking more people up, and the bus gets fuller."

With their three daughters in tow -- ages 5, 9, and 10 -- the bus is full indeed, and with the touring and joint performing, Hill admits that a little time apart, even in a happy marriage, is a must.

"We travel with a lot of people," says Hill in a separate interview. "I have my girl time in the dressing room, so that's kind of our alone time, which is good, it's healthy."

So healthy that they're ready to split up. At least when it comes to touring.

"We can never say never," says Hill to the possibility of another joint jaunt down the line. "But for the near future, no. It's one thing for one of us to be working, but both of us working the kind of schedule that you have to keep when you're touring like this is just not possible, and it's not fair to [the kids]."

With his wife or solo, McGraw is just happy to perform for his fans with his band the Dancehall Doctors, some of whom have been with him for more than 15 years. "I can remember being in a club for seven nights with probably 50 people a night in there, and to look out and see what we're doing now is pretty cool."

Tim McGraw and Faith Hill are at TD Banknorth Garden with Lori McKenna tomorrow and Friday at 7:30 p.m. Tickets are $50-$89.75. Call 617-931-2000 or go to ticketmaster.com.