In the late ’30s, while the younger generation was jitterbugging to swing bands, their parents (and their parents) were still flocking to old-fashioned, turn-of-the-century operettas, as produced both by Broadway and by Hollywood. Some of the more enterprising jazz stars of the era wisely exploited the incongruity when they began swinging numbers like Artie Shaw’s high-octane “Softly as in a Morning Sunrise.” One extreme example is a jive-talk version of “When I Grow Too Old To Dream” recorded by the Cats and the Fiddle in 1939, only four years after it was introduced in the film “The Night Is Young.” The Cats deflated the sentiment of both Sigmund Romberg’s melody, by putting it in relentlessly fast 4/4 swingtime, and Oscar Hammerstein’s lyric, by interjecting such wiseass asides as “if you’re not too big and fat to remember.”

Having grown up with the jive version, I didn’t think anyone could get me to take the song seriously again — but I was recently delighted to be proven wrong. “Too Old To Dream” was the first- act highlight of Monday’s concert, “A Night at the Operetta II,” which opened the three-night Summer Broadway Festival, produced by Scott Siegel, majordomo of the other Broadway-cabaret events at Town Hall, including the long-running Broadway by the Year series. The fine Irish tenor Bill Daugherty and the highly esteemed Broadway soprano Christine Andreas delivered it with nary a chuckle, total conviction and — and — notwithstanding the first line of the verse (“We have been gay”), sang it completely straight. It achieved Mr. Siegel’s purpose: to remind us why operetta was so popular for so long, even into the age of bebop and mature book-driven musical theater.

The answer is in the form’s especially lush, even soaring melodies, and the straightforward sentimentality of the texts. In general, operetta is a lot like opera, except that you can usually understand it. The focal point of American operetta, which injected a note of Yankee attitude into British (Gilbert & Sullivan) and German-speaking (Straus & Lehar) precedents, was the composer Victor Herbert (1859-1924), who wrote more than 43 works in the form, and, unlike such successors as Jerome Kern and Romberg, didn’t live long enough to make the transition into musical comedy. The Town Hall program included most of the Herbert’s durable hits: Brian Charles Rooney and his rather extreme tenor tackling “Ah! Sweet Mystery of Life” (not written for “Young Frankenstein”), Mr. Michaels basso-ing “Thine Alone,” and soprano Karen Murphy re-creating “Kiss Me Again” (a rare Herbert song recorded by Frank Sinatra) as originally introduced in the 1905 “Mlle. Modiste,” as part of a larger number called “If I Were on the Stage.” “Indian Summer,” derived from a piano piece, was actually introduced as a song in 1939 (15 years after the composer’s death), but Mr. Daugherty sang it as if it were heard on the stage 20 years earlier.

A primary thrill of operetta is pure chops: You want to hear stratospheric tenors and sopranos belting out high C’s — Mr. Daugherty and Mr. Rooney shot a few notes into the rafters that still haven’t come down — produced mostly without aid of amplification. But there are still plenty of laughs: Funnyman Jason Graae can always be counted on to provide the big comedy moment in an all-star concert. Equipped with top hat, tailcoat, and cane, he made like a cross between Maurice Chevalier and Jerry Lewis in “Très Parisienne” (from “The Merry Widow”), his fractured franglais and Gallic goofiness accentuated by four dancing gigolos. The only bit that left me cold was a rather creepy love duet on “Only a Rose” (from “The Vagabond King”) by Mr. Daugherty, singing tenor, and Mr. Murphy, employing a disconcertingly flawless soprano-falsetto. He didn’t miss a note and it wasn’t played for laughs (which might have worked), but overall it had the effect of going to bed with a woman and waking up with a drag queen.* * *

Marilyn Bergman, ace lyricist and president of the American Society of Composers, Authors and Publishers, has spoken of the difference between poetry, which is intended to be read silently to oneself, and song lyrics, which are meant to be sung to an audience. The celebrated American poet Nikki Giovanni recognizes no such distinction, as the exceptional singer Capathia Jenkins and composer-guitarist Louis Rosen showed in a set at the Iridium on Tuesday and in a new album, “One Ounce of Truth: The Nikki Giovanni Songs,” on PS Classics. Ms. Giovanni’s poems are so rhythmic and conversational that it’s hard not to hear them as music: “Telephone Song” re-creates a precocious dialogue between two little girls (“You hang up! No, you!”) and “I Wrote a Good Omelet (After Loving You)” is a riff on a 1949 Tony Martin hit entitled “I Said My Pajamas (And Put on My Prayers).”

Ms. Jenkins is well-known to theatergoers for her superb job in both “Caroline, or Change” and “Fame Becomes Me.” In the latter, she played the “big black lady” who “stopped the show,” but her voice isn’t big so much as sweet and radiant. She’s charming on Mr. Rosen’s lightly Latin, polyrhythmic “The World” and displays plenty of maternal warmth on the lullaby “Kiss a Frog.” The sole false note was on “The Black Loom,” which, as with any tune dedicated to Nina Simone, was highly confrontational — too much for Ms. Jenkins’s lovable disposition. Mr. Rosen’s own songs, with his words as well as music, tend to pale in comparison beside Ms. Giovanni’s more accomplished texts.

But overall, nearly all of Ms. Giovanni’s words, which also utilize pop-song-style repeated phrases and parallel construction, fit smoothly into Mr. Rosen’s melodies. His setting of “That Day” compares well with an earlier setting for the text recorded definitively by Dianne Reeves. Indeed, among living songwriters, possibly only Marilyn and Alan Bergman themselves could do better.

The Summer Broadway Festival continues for the next two Mondays with “Broadway’s Rising Stars” (July 21) and “All Singin’ All Dancin'” (July 28).

Capathia Jenkins and Louis Rosen return to the Iridium on two more Tuesdays (July 29 and August 5).