A large classical music institution, on the eve of a major anniversary, suddenly loses its beloved music director. How does the show go on?

This was the question that faced the Cathedral Choral Society on Sunday afternoon. In June, J. Reilly Lewis, who had led the group for 31 years and seemed boyishly healthy at 71, died suddenly of a heart attack, leaving Washington’s classical music world reeling — especially the two groups he led, the Cathedral Choral Society and the Washington Bach Consort. 

Sunday’s performance at Washington National Cathedral was not only the first time the chorus had performed since Lewis’s death but also the start of what Lewis had planned as a special season of celebration of the organization’s 75th anniversary. Lewis, the chorus’s second music director in those 75 years, declared the season “requiem-free,” meaning that he was avoiding a lot of the standard symphonic-choral fare. It’s poignantly ironic that the whole season has become a sort of requiem, to him — and that, rather than celebrating the long tenure of a beloved music director, the chorus finds itself in search of a new one. 

It wasn’t the kind of beginning anybody had in mind. But the onstage forces responded to the emotional challenge with one of the most vivid performances I’ve heard from them. Lawrence Loh, who has served as assistant and associate conductor with the Dallas and Pittsburgh symphony orchestras, stepped in adroitly to lead a big, eclectic program that paired Saint-Saëns’s “Organ” symphony with the Berlioz “Te Deum” — just the kind of overambitious sprawl in which Lewis exulted. And the performance captured the exultation, particularly in the “Te Deum,” which was a big, glorious wash of sound: a fitting tribute. 

The Cathedral Choral Society has been on a track, for the past season or so, of improving its game, but it’s had its share of administrative and musical problems over the years. One is the cathedral itself: a huge space through which sound powers like a tank, mighty but hard to turn quickly. On Sunday, in the Saint-Saëns, little string figures were like markings on the surface of a behemoth in motion. But the blasts of organ (played by Todd Fickley), given a slightly devotional air in this setting, rang down the nave in stained-glass waves of color.

The “Te Deum” was the big choral piece on the program, and the singers, joined by the cathedral’s children’s choir, sang mightily. They burst out in jubilation in “Tu, Christe”; provided a halo around the solo line of the tenor Patrick Kilbride, a worthy, sweet-voiced, last-minute replacement for the scheduled soloist in “Te ergo”; and illustrated the threat of darkness in the final “Judex crederis” before thundering to a close. 

One modification was made to the program: It opened with a Bach aria, “Schlummert ein, ihr matten Augen” from the cantata “Ich habe genug.” Laura Choi Stuart, the soloist, offered a lilting thread of sound atop this memorial to Lewis through his favorite composer — another sign of how well the chorus managed the tricky balance between sadness and celebration. The future is unclear, but with a group of guest conductors jumping in to help out, the chorus’s current season could be one to watch. 

The Cathedral Choral Society’s next performance is its “Joy of Christmas” on Dec. 9 and 11, led by Joseph Flummerfelt.