Renee Fleming leads a truly glamorous life. She jets around the world, packing major opera houses everywhere she lands. She kicks about town in high-end Japanese sportswear, and at night changes into couture gowns custom made by Giancarlo Ferre and Oscar de la Renta.

But no matter how grand this diva – in the proper, pre-Whitney Houston sense of the word – can appear, she has her secrets. Here’s one: She loves to talk about hedge funds. Really. “I meet a lot of very successful business people. I sit there and hang on their every word,” she told me. “I know as they’re describing hedge funds to me they think I must be bored, but I’m not. It fascinates me.”

It sounds unusual to hear that from an artist, but it’s exactly the sort of thing that defines the personality of this Rochester, N.Y., native: open, interested, and real. This is not something audiences always get to see. When she takes the stage in recitals – as she will tomorrow at Carnegie Hall – she is showcased like a fine jewel. In operas she’s often in full 18th-century costume, plus wigs.

But on a normal day, in person, in New York City, she’s a down-to-earth, single mother of two and very much a woman’s woman. She shows that side of her a bit in her charming book “The Inner Voice,” forthcoming from Viking. But she did even more so in a recent interview during which the talk ranged from her work and life to her appreciation of fashion.

Ms. Fleming studied music at Juilliard, SUNY Potsdam, and the Eastman School of Music. She became known as a specialist in Mozart, coming to prominence in 1988 with the opportunity to sing the role of the Countess at the Houston Grand Opera. “I think I debuted at six theaters in the ‘Marriage of Figaro,’ which at the time was frustrating,” she said. “Why couldn’t I be singing Musetta or Mimi in ‘La Boheme.’ Why couldn’t I be singing something easy?” (Having said this, she immediately took it back, out of superstition at the thought of ever calling anything “easy.”)

Gradually, she made a name for herself. When she looks back, she said, she finds that there were three main turning points in her career. First was her 1993 performance of “Armida” in Pesaro, Italy. “I really haven’t sung much in Italy since then, but what happened was that Europe suddenly said, ‘Hmm, not bad.'” Second was working with Sir Georg Solti and Decca records, which has been her label since 1995. “My relationship with the public in the U.K. and France was all from Solti,” she said.

Third was opening the Met’s season with a performance of “Otello” alongside Placido Domingo in 1995.

On the day I met Ms. Fleming, she had just been to Mr. de la Renta’s runway show at Olympus Fashion Week; naturally the conversation turned to sartorial splendor. Ms. Fleming is in the enviable position of having regular need of couture gowns. During a year of touring she gives anywhere from 40 to 60 orchestral or recital performances – and for each one she turns out spectacularly swathed in luxurious eveningwear.

In 1998, Ms. Fleming established a relationship with designer Giancarlo Ferre, who has almost exclusively created her concert gowns. “He understands that I have to travel with the dresses and they have to hold up to that,” she said. “He also understands that I can’t wear a sleeveless strip dress.”

Like an athlete, Ms. Fleming chooses attire to facilitate her performance. “A lot of the things I wear have built-in corsets or a structure that’s much more solid than one would expect in an evening dress,” she said. “It helps me sing. It helps my breath and makes me feel more supported.” Though the singer and designer will discuss styles, they don’t need a lot of back-and-forth anymore. “These gowns appear on my doorstep, virtually perfect. No fittings,” she marveled.

For this year’s tour, Mr. Ferre has created two dresses. The first features blue lace embroidered with Swarovski crystals; the other is made of black rauched jersey and lace. We’re likely to see one of them at Carnegie Hall, but don’t look for both in one evening. “I don’t usually change clothes. That’s kind of a step too far,” she told me. “It loses the integrity of the evening. You don’t ever want people to think that the dress is more important than the concert.”

The concert dresses do give the audience something gorgeous to look at as well as listen to at a recital, though. Likewise, the red Oscar de la Renta dress that she posed in for her new CD of Handel arias. She’s also performed in gowns by Issey Miyake, such as the silver pleated number she wore in a Opera News cover photo.

Unlike most celebrities, who wear a dress once and then discard it, Ms. Fleming wears hers night after night: “After a European and American tour, they practically disintegrate.”

As for her everyday clothes, Ms. Fleming is a die-hard devotee of Yoshi Yamamoto and Mr. Miyake. “I go crazy in those two stores,” she said, adding that she does most of her shopping in Japan and Paris. Do they close the shop for her? “I never ask,” she said, and the thought “why bother?” seemed to flutter across her face.

Speaking of that face: At rest, Ms. Fleming has a somewhat serious mien. She could be a hassled soccer mom – albeit one wearing black pleated Issey Miyake pants, big dangly earrings (borrowed from a jewelry-rich girlfriend, she told me), and lots of black eyeliner. But when she smiles she is a beauty. Watching Renee Fleming break into a grin is like catching a cool breeze on a hot day. When it’s gone, all you want in the world is to make it come back.

What she wears on her face is of no small importance in her line of work. This singer does her own makeup for concerts, and is partial to products by Laura Mercier, Chanel, MAC, and the new line of cosmetics from make-up artist Scott Barnes, who recently worked with Ms. Fleming on a magazine shoot. “Its coming out at Saks, and I can say already it’s beautiful stuff,” she said, adding with a guilty sigh: “I love make-up.”

Ms. Fleming and her daughters live in Manhattan, and the girls (aged 9 and 12) attend private school here. But even with all the fancy clothes and make-up, when Ms. Fleming needs to shop for them, she makes a trip home to Rochester: “We go to the malls and get everything at once.”

Like other working mothers, the opera star has felt a bit of a chill from other parents at times. “Sometimes people jump to conclusions about me maybe being a not very interested parent,” she said. “Every once in a while I’ll get that kind of attitude.” But more frequently her fellow parents are ignorant of who she is: “Most people don’t pick up on it. So that’s great. I can just be myself. Every once in a while, someone is intimidated.”

Such treatment seems to annoy, rather than flatter, this soprano. Which certainly goes against the type. But Ms. Fleming is entirely open about her diva moments – which she writes about with humor in the book. “If I’m nervous about something coming up, I’m 100 times more sensitive to everything around me,” she admitted. “I’ve been known to put napkins around my neck in fine restaurants. So, yeah, I’ve had my moments.”

There’s much more to the book than self-deprecating jabs at diva-dom. Ms. Fleming’s career, though thriving now, was an uphill battle. She had trouble with high notes. She found auditions grueling – and had to struggle with presenting herself correctly in them. “People often think, ‘She’s so lucky. She was born with it.’ So I thought, let’s just spell it out,” she said of her decision to write her autobiography. “I do have colleagues for whom it was not so difficult. For me it was particularly a savage road.”

Knowing the struggles she encountered along the way makes her less easy to envy when she says: “I don’t lack for anything right now.”