She doesn’t sell out the Metropolitan Opera, but she has one of the biggest recording careers of any active opera singer. She doesn’t do arena concerts, but she did make an album with Elvis Costello. Swedish mezzo-soprano Anne Sofie von Otter isn’t a superstar. She just has one of the most successful careers, and the longest, of any classical singer today.

Von Otter, 60, is coming to Washington twice this month, in just the kind of repertoire for which she’s known. This week, she’ll sing Mahler’s Third Symphony with the National Symphony Orchestra — one of the pieces she has done most. On Nov. 17, she’ll give a recital at the Library of Congress with harpsichord and the long-necked lute cousin known as theorbo, focusing on baroque music, Arvo Part, and Simon and Garfunkel.

“I can’t help myself,” she said, self-deprecatingly, by phone from Europe last month. “I like to do my pop ballads. There’s so much in common with baroque music. There are singer-songwriters of the baroque era, like John Dowland, and a lot of the songs have the same kind of harmonies, the same pattern.” Simon and Garfunkel, she added, “works very well with harpsichord and theorbo.”

Not all opera singers have huge, powerful voices. But the ones who don’t, when they hit mid-career, often find themselves chafing against their vocal limitations. What do you do if you’re a singer who will never be able to sing Puccini (much less Verdi or Wagner) in an opera world that prizes that composer?

Von Otter isn’t the first lyric mezzo to assess her resources, find roles that fit her and sing for decades — Frederica von Stade, the beloved American mezzo, comes to mind. But few singers have addressed themselves to such a diverse range of music. One of von Otter’s early recording successes was a 1993 CD of songs by the Norwegian composer Edvard Grieg, not usually a bestseller. One of the most recent was “Douce France,” a compilation of French popular songs that won the 2015 Grammy for best classical vocal solo. Other collaborators and composers have included Cécile Chaminade, Brad Mehldau and ABBA’s Benny Andersson.

Swedish mezzo-soprano Anne Sofie von Otter. (Ewa-Marie Rundquist)

“The ABBA CD is the one I’m least happy with,” says von Otter. “It was a lot harder than I thought to do something with the actual material.” For the original ABBA recordings, Andersson told her he would spend, she says, “two weeks in the studio with the group and instruments, on just one song. No wonder the sound is so specific for ABBA. And without that sound, some of the songs were really hard to do anything with. The musical material is quite small. [Whereas] Elvis Costello had much more idea what would suit my voice.” Their CD, “For the Stars,” remains one of her most successful recordings.

To make this kind of thing work, it takes a certain kind of voice. A singer with a lot of vibrato — the opera singer’s signature vocal vibration — can sound silly or affected in pop-song repertoire. Von Otter’s voice is notably straightforward; she’s able to modulate it to fit into a range of styles without a lot of fuss. This doesn’t mean it’s not capable of great beauty and great subtlety, particularly in the art-song repertory. But in 2013, when she appeared at the Kennedy Center under the auspices of the “Nordic Cool” festival, I wrote that “she’s like the singer next door; she seems as though she just happens to be sharing with you a couple of songs she likes.”

Also, “it’s so important how [the songs] are arranged,” von Otter says, “if you’re going to step outside your classical [bubble]. People tend to over-arrange. There is always so much going on: Flutes and angels and choirs going on in the orchestra, constantly drowning the songs in a lot of noise. [Finding] the right colors is a lot more important.”

It also takes the right collaborators — such as the pianist Jonathan Cohen and the lutenist Thomas Dunford, who recently impressed in a baroque Persian jam session at the Phillips Collection and who will appear with von Otter at the Library of Congress. Von Otter, at this stage in her career, can attract blue-chip colleagues (such as the pianist Emanuel Ax) and has a nose for young talent. For her next album, “For Sixty Cents,” she is making a foray into contemporary music, which — unlike most classical artists noted for diversity — she has hitherto largely avoided. “Some contemporary music around is not my taste,” she says, “but some of it is. I love John Adams. Well, who shall I do it with? A whole orchestra is too expensive, and just piano is not fun.” She decided to look for “a youngish, cool and hip string quartet,” and landed on Brooklyn Rider — one of the most prominent contemporary ensembles.

Most important, perhaps, it takes an artistic sensibility that is at once sensitive and voracious. Von Otter, unlike some singers, has not deliberately carved out a maverick role; she was a remarkable Carmen at Glyndebourne and has excelled in Mozart and Strauss at the Metropolitan Opera, among many houses and many roles. But she has never gotten stuck repeating past successes — one reason that she has been able to sing through her sixth decade and into her seventh without diminishing her activities. Indeed, she says, she wants to work more in the next few years to take advantage of the vocal time she has left.

“I think there is a sort of chip in my brain I was born with,” she says. “Of course it’s curiosity, but also restlessness. I have a lot of energy, and I’m not the person who likes to do the same thing over and over again. I’m a short distance runner. I could never run a marathon, but I run lots of 100- meter things. I spend a period of time on a certain composer or certain colleague, and then I go on. There’s so much out there.

“To have a long career,” she adds, “you have to be very creative. And I guess I am.”

Anne Sofie von Otter appears with the NSO at the Kennedy Center Concert Hall in Mahler’s Third Symphony on Thursday, Friday and Saturday, and in recital at the Library of Congress on Nov. 17.