In April, Norman Scribner said goodbye to Washington. On Wednesday, Washington is going to say goodbye to him.

Scribner, 76, has for the last two years been taking a long farewell from the Choral Arts Society, the group he founded 47 years ago and from which he is retiring at the end of this season. With a $2 million annual operating budget and more than 180 singers, the Choral Arts Society is one of the biggest choruses in Washington. Scribner’s successor has been named (Scott Tucker, of Cornell University); he’s conducted his last concert (the Brahms Requiem in April); and now the other leaders of Washington’s choral scene are convening to send him off. Among Wednesday’s performers at the National Cathedral are J. Reilly Lewis, of the Cathedral Choral Society, and Robert Schafer, who for 36 years led the Washington Chorus and now heads the City Choir of Washington.

Indeed, this is a goodbye to more than Norman Scribner. The evening is a farewell to a whole era of choral life in Washington: a time when the city had four big symphonic choruses with million-dollar budgets led by four charismatic conductors performing the great works of the choral repertory.

Only three of those four choruses remain; the Master Chorale closed in 2009, a victim of the economic downturn. Still standing are the Cathedral Choral Society, the Washington Chorus, and Choral Arts, but each is undergoing its own process of transformation. The Cathedral Choral Society, the oldest of the group, has been led by Lewis for decades, but is currently in the midst of tremendous turnover of its administrative staff, and is at something of a crossroads. The Washington Chorus is the farthest advanced in its second chapter; its 40-something music director, Julian Wachner, has been working energetically to give it his own stamp, including everything from orchestral repertory to new music. (On June 23, the group will present the world premiere of a multimedia folk opera by Paola Prestini, “Oceanic Verses,” which will go on to New York and, in 2013, London.) And the Choral Arts Society is now also looking toward a new beginning.

Make no mistake: Washington will always have an abundance of choruses, and in many ways its choral life is richer than ever. Washington seems to be a town that naturally attracts people who want to sing in choruses: some mixture of group-think and civic pride, of participatory zeal and a genuine love of music. Large and small, Washington’s choruses have no trouble finding singers — even the newest arrivals on the scene, like the Washington Master Chorale, a semi-professional chorus of 65 voices founded in the wake of the Master Chorale's 2009 closing (with some of the same singers).

“Now more and more singers are finding out about the choir,” says Thomas Colohan, the group’s founder and music director, “we have a backlog of people; I don’t have to announce [auditions]. I have a list of people on the substitute list.”

But perhaps precisely because there are so many singers in Washington, the city’s choruses end up being a mirror of the city’s current society. Today’s choral singer is likely to be a recent college graduate still basking in happy memories and strong associations with his or her glee club — which taught, the executive director of the Choral Arts Society, Debra Kraft, pragmatically observes, “discipline not only musically, but commitment to an organization.” While happy to take part in the city’s traditions, they’re interested in a wide range of music, from Bach to pop, new music to gospel. And there’s a wide range of choruses around to cater to their specific interests, from the Gay Men’s Chorus to the Cantate Chamber Singers.

Even the old-guard choral directors have had to learn a new kind of flexibility — particularly Robert Shafer, who in 2007 was relieved of his role as music director of the Washington Chorus before he was entirely prepared to relinquish it. Shafer went out and founded the City Choir of Washington, which performs a wider range of music, including pops concerts, on a fraction ($250,000) of the Washington Chorus’s $1.4 million budget. As for his successor at the Washington Chorus, Wachner, he’s traveling back and forth from Washington to New York, where he leads the music program at Trinity Wall Street — wearing two hats in a way that none of his predecessors in Washington did.

But Washington’s largest remaining choruses are all being forced to strike out in new directions. While there’s a steady supply of singers, there isn’t the same steady supply of listeners.

“Years ago we could program a Verdi Requiem and sell it out two weeks in advance,” says Dianne Peterson, executive director of the Washington Chorus. “That’s not true any more.”

With decreased funding and dwindling audiences, choruses are having to experiment with a wider range of collaborations, move more forcefully into arenas like outreach and education. The second question funders ask, Peterson says — after asking what makes the Washington Chorus different from the city’s other big choruses -- is, “What are you doing to collaborate with other organizations?” She adds, “I don’t think we can all be isolated any more.”

“I like those challenges,” says Debra Kraft, executive director of the Choral Arts Society, “because I think it keeps you fresh. It keeps the creativity high. I’m sure that’s what led us to thinking about all sorts of ways to work with WPAS, because they’re in the same place. It’s exciting: we think alike, can augment our stats; we feed off each other.” Choral Arts is going to Lisner Auditorium next year with a community concert called “Latin Rhythms,” while the Washington Chorus is doing a similar outreach project with the singer-songwriter Melanie DeMore.

Flexibility and education aren’t exactly a break from tradition: more a continuation of it. Scribner and his fellows were — and are — eminently pragmatists. They went out and founded their own choruses and watched them become institutions. They commissioned and embraced new work. Scribner is associated with the world premiere of Leonard Bernstein’s “Mass” in 1971, which opened the Kennedy Center, and he continued to premiere new pieces until the penultimate year of his tenure; while the Cathedral Choral Society has had a dedicated commissioning fund since 1991. At his new City Choir of Washington, Shafer is preparing for next season's premiere of a work by John Tavener, perhaps the most successful choral composer alive.

These men were and are also generous colleagues who encouraged younger artists to spread their wings. Eleanor Epstein, who sang under Scribner in the 1970s, recalls him cheering her on when she founded her own chorus devoted to Jewish music; her group, Zemer Chai, is now celebrating its 36th anniversary.

The fundamental humility and adaptability of its old guard has laid a great foundation for Washington’s choral tradition to move forward even in straitened economic times. Indeed, the very adaptability of volunteer choruses may render them one of the better models in classical music for survival in the future: people who want to sing will find a way to do it, and find the money to pay for it.

But all the evidence seems to point to leaner, tighter fiscal models in future. And Washington is filled with more and more serious smaller choruses that artistically and organizationally are giving the old guard a run for its money. Or perhaps they’re simply expanding the playing field. Choralis, a 100-voice semiprofessional chorus founded in 2000 (which is also currently looking for a managing director), has established a Greater Washington DC Area Choral Excellence Award, which it hands out at its annual spring gala: a fine way to build camaraderie while establishing the newer chorus’s place at Washington’s choral table.

So far, the award has gone exclusively to the old guard: Shafer, Lewis and Scribner have been the three recipients to date. But the mood at this year’s gala, honoring Scribner, was “collegial,” says the Washington Master Chorale’s Colohan. “There were about 15 of us [choral directors] there.” That’s a bigger old-boy (and old-girl) network than Washington used to boast; and they are working together in more ways — the Washington Master Chorale, for instance, is teaming up with a small group called Words and Music to commission a new piece for next season from the music director of the defunct Master Chorale, Donald McCullough.

Meanwhile, at least one executive envisions a whole spectrum of Washington choruses coming together for a single concert series at National Presbyterian Church. If more directors are encouraged to work together in more ways, Scribner’s legacy is a fine one indeed.

“The Legacy Celebration” honoring Norman Scribner takes place at the National Cathedral on Wednesday at 7:30 p.m