There are many ways you can measure the high-water mark of modern dance, but one method might be to pinpoint the moment at which its European predecessor, ballet, started inviting the distinctly American artform into the highbrow fold.

If you can settle on when that moment was.

For Alicia Adams, the Kennedy Center’s vice president of international programing and dance, the re-merger happened one night in New York in 1984, when ballet dancer Rudolf Nureyev appeared as a guest with the company run by then 90-year-old modern dance pioneer Martha Graham.

But it could have come two years earlier, when American Ballet Theatre performed “Duets,” a work by Graham’s protégé Merce Cunningham. Or maybe it was in 1973, when the Joffrey Ballet premiered Twyla Tharp’s Beach Boy boogie, “Deuce Coupe.” Or in 1970, when Alvin Ailey choreographed his first work for ABT.

Whenever you start counting, there is broad agreement that from the later decades of the 20th century forward, no proverbial line between modern and ballet has been drawn on the marley flooring of a dance stage.

“It’s an old story,” Adams said. “A long time ago, the line between ballet and contemporary dance became blurred.”

Over the next two weekends, Washington audiences will have a chance to see programs that demonstrate just how fuzzy that line is. On Wednesday night at the Harman Center for the Arts, the Washington Ballet will present its “Jazz/Blues Project,” featuring works by Trey McIntyre and Annabelle Lopez Ochoa, two relatively young choreographers known for flying back and forth, across continents, creating works for ballet and contemporary companies.

Meanwhile, the Kennedy Center will host a company this week that offers ballet in its truest 19th-century form: Russia’s Mariinsky, performing “Swan Lake.” Things will get shaken up starting Feb. 4, however, when Alvin Ailey American Dance Theater comes to town for its annual six-day run. After the company’s New York season, all the buzz is about the newest work in Ailey’s repertory: British choreographer Wayne McGregor’s “Chroma.”

Commissioned in 2006 by London’s Royal Ballet, “Chroma” is performed on this continent only by the Boston Ballet, the San Francisco Ballet and the National Ballet of Canada. Now Ailey, one of the United States’ leading modern dance company, is earning praise for this abstract, toe-shoe-free ballet performed to orchestrations of music by the rock band the White Stripes. The company also has revived “The River,” a 1970 piece that company founder Alvin Ailey created for ABT. Last season, the company added to its repertory Jiri Kylian’s “Petite Mort,” a long-lined lyrical classic that is nearly always performed by ballet companies rather than modern dancers. All three will be included on programs at the Kennedy Center.

Ailey seems to be offering balletomanes a program they’d love, and the Washington Ballet one with broad appeal to modern-dance fans. And yet, statistics suggest that the majority of dance fans will choose one or the other, and not because they’re on a budget. Last season, only 18 percent of people who bought tickets to a ballet at the Kennedy Center also bought tickets to performance that was labeled “contemporary dance.” That doesn’t mean contemporary dance is unpopular. On the contrary, over the past 10 years, the Kennedy Center has had a 50 percent increase in subscribers to its contemporary dance series, while the number of ballet subscribers is down slightly, mirroring national trends.

The Kennedy Center declined to release exact subscriber numbers, but clearly a paradox is at work: Dance company directors and choreographers have tastes that are far more mutable than the average Washington audience member. Talking about the divide between modern dance and ballet may be an old story, but it’s still a topic of conversation. The Washington Post spoke about the perceived ballet vs. modern divide with three choreographers involved in the Washington Ballet and Ailey performances. (Their comments have been edited and condensed.)

Robert Battle

Robert Battle became the third artistic director of Alvin Ailey American Dance Theater in 2011, and has worked to stretch and diversify the company’s repertory. The Juilliard School graduate is a former dancer with Parsons Dance Company and a former director of Battleworks Dance Company.

“My take on it is how closely related ballet and modern are,” he said. “At ballet’s beginnings, it was avant garde, for its time. And its rules kept getting broken, by Nijinsky and later by Balanchine. To me, modern dance came out of that, breaking the rules, just maybe more severely. It was about taking off the toe shoes and conveying the weight of the human condition, as opposed to being ethereal.

“But they are still closely related. When you see ‘Revelations,’ you can see arabesques and all these other positions with French terms. Without ballet, you can’t have the modern. What struck me about ‘Chroma’ wasn’t just the ballet that was in the work, but the use of the torso. It was shocking, in a way, to see the Royal Ballet dancers move that way, and it flipped the coin. There are contortions you don’t expect to see in ballet.

“I kept watching ‘Chroma’ until I could see my dancers in it. I won’t hide the fact that I was looking for the element of surprise, to shake things up a little bit and do the unexpected. But I saw so much in ‘Chroma’ that was also Ailey’s own vernacular. If you look at some of the movement, and the intensity of it, it reminds me of Ulysses Dove’s work — the fast chainez turns into pirouettes. I loved the attack of it. I loved the excess of it, and I thought it would be a nice fit.

“So much of the training that my dancers have is informed by ballet. They take ballet along with the modern classes. You really see that in the way training has developed. Certainly, some of my dancers have done work with ballet companies. It’s in their DNA, and doing ‘Chroma’ was a way of turning up the volume on that.”

Val Caniparoli

Choreographer Val Caniparoli’s works are in the repertories of 45 dance companies. He has been affiliated with the San Francisco Ballet for more than 40 years as a company member, choreographer and character dancer. His best-known ballet, “Lambarena,” is danced on pointe, but performed to both Bach and traditional African music, with references to African dance. The Washington Ballet will revive his 2000 commission “The Bird’s Nest,” which is set to music by Charlie Parker, starting Wednesday.

“The whole ballet/modern crossover thing is a mystery to me, at least, as it pertains to my work,” he said. “Directors will call me and say, ‘I want to give you a commission. Can you please make it on pointe?’ Pointe. Pointe. Pointe. And I say, ‘Of course.’ They need me to do it, because other choreographers aren’t. If a company is doing a mixed-rep program, the dancers still need to get their pointe work in, in between all their ‘Swan Lakes’ and ‘Giselles.’ So much of my work I get because I do it on pointe, even though it may look like ‘crossover.’ It’s the only thing I know. I can only do what I know, and I don’t know modern dance extensively.

“The San Francisco Ballet, in the 1970s and 1980s, was very eclectic and not strictly classical. That’s how I was brought up, so crossover is not new to me. I can’t believe “Lambarena” is 20 years old. Oh my God. It was a revelation, and my choreography took a new direction at that point. I was studying African dance, and I was told to just relax, not be so regimented. It had an impact on me, but the choreography is still interwoven into that classical base.”

Annabelle Lopez Ochoa

Belgian-Colombian choreographer Annabelle Lopez Ochoa grew up dancing at the Royal Ballet of Flanders but began her professional career with a jazz dance troupe. As a choreographer, she has become a global commodity. Her work was seen in Washington last month, when Ballet Hispanico performed “Sombrerísimo.” That was a light ensemble piece for the company’s men, but she also is known for her serious pointe pieces, including “A Streetcar Named Desire” for the Scottish Ballet. Later this year, she’ll become the first outside choreographer to receive a paid commission from the National Ballet of Cuba. Her new work for the Washington Ballet is called “Prism,” and it’s set to a piano score — which will be performed live — by Keith Jarrett.

“I am a contemporary choreographer who is in love with the aesthetic of the pointe show. I was not going to have this new Washington Ballet work be performed in toe shoes, but I changed my mind a week into rehearsals, because they look so beautiful on pointe.

“People dream away when dancers are on pointe shoes, because it’s so supernatural. It’s abstract. But contemporary dance reflects the society where we are today, more than a piece by Balanchine. It can be about themes, like loneliness. It’s much more raw, and the bodies of the dancers are more like us. Ballerinas are elegant. The audience is asking for that distinction: What I am paying for? That’s why [places such as the Kennedy Center] make a distinction between contemporary and ballet.

“In Europe, people like to be surprised more. The innovative thing is more fashionable here. I like the variety. That I am not put into a box. That’s a bit of a problem, because people don’t know what to expect. My tools are the dancers, and I adapt to what I see. I don’t want to label myself into one form of movement, to one energy. And I hope that’s how my career continues. I like being able to view ballet as just dancing in a very high-heeled pair of shoes.”

Ritzel is a freelance writer.

Alvin Ailey American Dance Theater

Feb. 4-9 at the Kennedy Center’s Opera House; 202-467-4600

Washington Ballet’s ‘The Jazz/Blues Project’

Jan. 29-Feb. 2 at Sidney Harman Hall, 610 F St. NW;

or; 202-547-1122