Many older hit musicals are ripe for revival—and then there are the others, now commercially unviable, with slim hope of seeing Broadway again. However, each year three such shows are lovingly revived for six performances each by the New York City Center Encores! series.

For 21 seasons this busy, successful not-for-profit has been bringing back long-unheard musicals with their original large orchestrations—which often means 30 musicians alongside a cast of another 30.

One such show is Frank Loesser’s moving and operatic The Most Happy Fella, a smash from 1956 that’s now just too much for Broadway.

“Most Happy Fella is a classic, but so big it does not get revived,” says longtime City Center Encores! sound designer and multiple-Tony-Award-winner Scott Lehrer. “After Guys and Dolls, it’s Frank Loesser’s best show, if not his best.”

At the other end there’s the ultra-lightweight Lady Be Good, the Encores! 2015 opener. This 1924 Fred & Adele Astaire show was the first true Gershwin Brothers collaboration, with great songs (“Fascinating Rhythm,” “Lady Be Good”) but a dated, silly book. However, at City Center Encores! music comes first, so a seriously dated book is no deterrent.

It’s about hearing these original scores in all their glory for the first time in decades, in the lovingly refurbished Neo-Moorish City Center. It’s a time machine for serious musical-theater fans. In fact, music so central to the mission that the big orchestra is positioned right up onstage.

Encores! is notable for working big but working fast. With the budgetary constraints of six performances, shows go from first rehearsal to opening in about a week.

“It is the X-Games of theater, like going back to summer stock,” Lehrer says. “The actors ask themselves ‘Can I learn my part in a week?’ But of course they do.”

And instead of tech-ing for weeks like on Broadway, tech is a day (or two). “It’s kind of fun. Guerrilla tech!” says Lehrer. “One day of tech, one dress rehearsal for 2,500 people and then we go. It’s exciting.” (And while quite busy with Broadway [Honeymoon in Vegas], Lehrer keeps coming back; Lady Be Good was his 50th Encores show.)

Despite the hectic schedule, they get Broadway’s finest: “The absolute best, whoever’s not busy with a movie or TV series, like Laura Benanti [TV’s Nashville; Gypsy Broadway revival] for Most Happy Fella. She was as good a Rosabella as has ever been!”

The male lead was Shuler Hensley (Young Frankenstein), just days from his Broadway run in No Man’s Land/Waiting for Godot with Patrick Stewart, and Ian McKellan.

Encores! also attracts big names from outside the theater world; film star John Turturro will make his musical-theater debut in the lead role of Zorba!, the final 2015 Encores! production, which takes place May 6-10.

Officially, Encores! are “concert versions.” Actors are often “on book”—holding, and sometimes using, scripts. (The audience expects this, and it can be played for clever laughs.)

However, 2014’s The Most Happy Fella was a Broadway-style production in most every sense, with exuberantly colorful costumes, full choreography and cleverly simple lighting and sets. Not one actor held a script.

The series has indeed come a long way. Their first production, 1994’s Fiorello!, was, “Bare bones, four RF mics, everyone on book,” says Lehrer, sound designer for that show.

The audio production has progressed but there is still an array of slim stand mics placed prominently downstage, something not seen on Broadway in decades.

While all principals now have RF head mics (up to 16 DPA 4061 and Sennheiser MKE 2s), the chorus has none, and uses the half-dozen AKG 391 mics at the stage lip. To make this old-school approach work, “I help re-block, move the softer voices in closer so everyone’s about two-to-four feet away when singing,” Lehrer explains.

As for singing without head mics, there’s no problem. “Vocal projection is still part of theatrical training,” Lehrer notes, cautioning that “there is sometimes so much stage noise, moving lights and sets. If you’re quiet, you’re barely above the noise floor.”

Lehrer uses the house system, which he consulted on with house sound engineer Augie Prosperi. It’s run with a Studer Vista 5 control surface with Lexicon FX Engine and Theatre Cue software. “The Studer is flexible and has immediately-fantastic sound, you just plug in a mic. It has a ‘straight wire’ feel, musical and open like there’s nothing between actor’s voice and the speakers.”

City Center has long been a showcase for d&b audiotechnik speakers, and the system, with a center cluster added last year, is all d&b. It uses the J12/J8 for center, C7 for left/right and the E Series and T10 for delay and fill.

Encores! productions do move on to Broadway, sometimes for spectacularly unlimited runs, such as Chicago, revived in 1994 and still going strong, and a recent successful Gypsy revival.

But Encores! isn’t a laboratory incubating for The Great White Way; their mission is presenting great shows and scores faithfully.

And part of that is using modern technology—and a low volume level—to “present the work with the sound seeming to come from the stage, so the audience hears the music closer to how it sounded ‘in the olden days.’

“However, we’re doing a fair amount of reinforcement,” Lehrer adds. “We’re able to make it sound transparent using the Outboard Electronics Timax 2 delay matrix to source sound to the stage more accurately. Broadway designers are doing this more now, but it works much better when you keep volume levels down.”

It does work. The volume is refreshingly low, the sound is clear and present and seems to come from the stage totally un-amplified, like stepping back in time. Critics and audiences agree, Encores! is theater magic, and smart sound design is one reason why.