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Tony Bennett sounds ageless. Concertgoers and critics walk away from his performances raving about the crooner sounding better than ever.

How does he manage to wow audiences at age 92?

In his usual gracious way, he shared his secret by e-mail. It draws on the bel canto technique, used by opera singers, that he was taught by the American Theatre Wing in New York in the late 1940s — long before he left his heart in San Francisco.

"I still remember," he wrote, "this cautionary tale that I was told back then about doing your vocal exercises: 'If you skip them one day, you know it; if you skip them two days, the band knows it; if you skip them three days, the audience knows it.' "

Like Bennett, who returns to Minneapolis July 28 for a concert at the Orpheum Theatre, singers need to take extra care of their voices as they get older.

Age 50 seems to be a turning point, according to University of Minnesota associate professor of voice Wendy Zaro-Mullins, herself a singer over 65.

Both women and men experience hormonal changes. Singers tend to lose vocal range because their vocal folds are less elastic and don't vibrate as easily. Moreover, medications — a reality for many older folks — can cause dry-mouth, an enemy of singing. (Read 10 tips for older singers here.)

Exercise matters

The importance of regular exercise can't be stressed enough. Different singers have different routines.

Rock and Roll Hall of Famer Darlene Love, 77, does kick boxing several days a week when she's not on tour.

Twin Cities singer/voice teacher Judi Vinar, 58, who tours with Bobby McFerrin's Voicestra, swears by her daily yoga workout.

Beach Boys singer Mike Love, 77, does transcendental meditation twice a day — double the prescribed 20 minutes. "That gives me a lot of energy and clarity and deeper rest and even deep sleep," he said.

Yes, sleep is also essential. Especially for singers on tour, who are challenged by changing climates as well as dry and germ-filled air on planes.

"Sleep is a big thing for my voice," said deep-voiced Righteous Brother Bill Medley, 78.

"Rest is the answer," declares New York cabaret great Marilyn Maye, who at 91 is still singing and conducting master classes.

Some singers try to clam up on performance days. "I had two throat surgeries where I had polyps and cysts taken off my vocal cords," said Lynyrd Skynyrd frontman Johnny Van Zant, 59. "So I asked Dwight Yoakam, 'What do you do to rest your voice?' He said, 'I don't do interviews.' "

Bonnie Raitt, 69, knows what Yoakam means. As someone who is hands on with all decisions in her career, the Rock Hall of Famer says that e-mail and texting have been a godsend, enabling her to communicate with her staff all day while preserving her voice for her nighttime gigs.

Voice professor Zaro-Mullins says it's actually OK to talk on show days because it helps warm up the vocal folds. But too much — or too loud — is a bad thing.

Bad, bad habits

Other singers have eliminated bad habits.

Veteran British rocker Terry Reid, 69, stopped smoking Lucky Strikes and gave up whiskey, too, so he could continue to live up to his nickname of "Superlungs."

"It all catches up with you. I quit everything I like," he whined.

Yes, booze is bad for vocalists, even for saloon singers like Frank Sinatra. Alcohol dehydrates them.

Hydration is essential. At least 64 ounces of water throughout the day — and up to 80 to 90 ounces (12 glasses) as you get older, advises Zaro-Mullins.

Like an Olympic competitor, a singer is an athlete with muscles, i.e. vocal folds, that need to be exercised and cared for. Proper technique is important.

Twin Cities singer Vinar, who has been teaching for 25 years, emphasizes three things: Breathe; don't over-sing (think of the microphone as an extension of your instrument), and don't sing really long phrases without refueling with air.

She also touts one aspect that is often overlooked: being in the right frame of mind.

"Your happiness is a huge factor — feeling good about your life, feeling good about the songs you're singing, feeling good about the gig," Vinar says. "Stress wears on us. It finds its way into the voice."

As with any athlete, warming up is important.

Zaro-Mullins, a teacher for 30 years, recommends starting with simple lip drills, then taking a break, followed by warm water and finally stretching the vocal folds with runs, octaves, etc. to enable the voice to transition between registers.

Not all Rock Hall of Famers follow the advice of vocal pros. Neither David Crosby nor Graham Nash — who both sound remarkably good at age 77 — does much to stay in shape.

"I don't have a vocal coach," Nash says. "I don't do exercise. I warm up a little bit before concerts but not much. I just sing. I've always been lucky."

Similarly, Crosby warms up by singing for 15 minutes.

Other legends, however, feel they need to work more diligently.

"I don't go very long without a coach," confided Joan Baez, 78. "A number of years ago, I started doing vocal therapy because I thought things were going wrong. It turns out: No, the vocal cords are doing what they do, which is get tired. They're a muscle. It takes a lot of practicing and doing everything in my tool kit. I keep reminding myself what the tricks are."

Get 'em while they're young

Even younger singers have sought help from coaches to learn how to sing properly.

Rock 'n' blues screamer Jonny Lang, 38, suffered from over-singing. About 20 years ago, he visited Boston instructor Mark Baxter, who has worked with Aerosmith's Steven Tyler and Stone Temple Pilots' Scott Weiland.

"He understands how to deal with people who beat their voices up, which is what I do pretty badly," Lang said. "He showed me how I could keep the tone I wanted while mitigating the damage and swelling of my vocal cords."

For Lang, a key is warming up before he sings, and "warming down" afterward — "10 to 15 minutes of light siren vocalizing [a vocal glissando]."

"It's usually the warming down that saves me the most the next day. It's like a marathon runner who has to jog or walk a few laps after the marathon to cool their muscles down."

For 47-year-old Broadway star Idina Menzel, it's a matter of discipline. No matter where in the world she's performing, she'll get on the phone with her vocal teacher of more than 20 years and do a 30-minute warmup. If the time zone makes it difficult, she uses a recording for warmups.

Menzel, who sometimes performs eight shows in a week, is prepared for all situations. If she's coming down with a cold, she uses steam to keep her system hydrated.

She even formulates a vocal approach in case she's performing under trying circumstances.

"When you're fighting a cold or you're singing outside in zero-degree weather and if there are areas of the song that might be difficult, I come up with different ways of singing. Then it doesn't feel like I compromised myself."

Finding a different approach is crucial to maintaining success as a singer ages.

"Your chops are going to fade one day. It's natural with age," says Grammy-winning producer Don Was, who has worked with such giants in their golden years as Willie Nelson, Mick Jagger, Van Morrison, Elton John, Neil Diamond and Gregg Allman.

Was encourages older singers to concentrate on phrasing and storytelling.

"Leonard Cohen had what you'd call a monochromatic voice and you wouldn't have considered him much of a singer," Was opined. "But as he got older, he surpassed his contemporaries. He infused every word with meaning. He was a brilliant singer.

"A lot of these guys I prefer as older singers. Look at Tony Bennett. He can still be riveting in concert. Sometimes aging separates men from the boys."

Twitter: @JonBream • 612-673-1719