“I like diversity in all parts of my life,” said Rob Fisher, the respected and beloved musical director of the Encores! musicals-in-concert series at City Center. “I need musical diversity.”

He’s going to get it. In January, Mr. Fisher announced that, following Encores!’ current season – its 12th – he would leave his post to take advantage of other opportunities. “The demands of Encores! were not allowing me to pursue other things,” he said.

Looking at Encores!’ willowy spring schedule, it’s hard to imagine how rigorous those demands are. After all, the program only stages three shows a year, none of them full productions, and each for a total of five performances. (The next, “Purlie,” runs March 31-April 3). Yet, Mr. Fisher insists he doth not protest too much.

“It has to do with the size the productions have become,” he explained during a rare free moment when he wasn’t rehearsing, performing, traveling, or sleeping (he was, however, eating). “They continue to grow and the pre-production leading up to them expands. It really is every day of the year now that I work on Encores! The summers are exploring what we might possibly do, which means after the 36 most obvious choices.” (Translation: the shows already chosen over the first dozen seasons.) He and Encores!’ artistic director, Jack Viertel, try to make their decisions by Labor Day. Then the creative teams are finalized, which leads to casting, which rolls up to the feverish week-long rehearsal period. “They’re like three Broadway shows,” he said. “It fills up the year. It really does.”

It’s hard for some not to view Mr. Fisher’s passing from the Encores! scene as nothing less than the end of a glorious chapter for the City Center series, whose mission of restoring the luster and reputation of forgotten musicals by presenting them in snappy, short-run concert versions has made it a treasured organization to musical mad theater fans and – same thing, really – drama critics. Through three artistic directors – Walter Bobbie, Kathleen Marshall, and now Mr. Viertel – Rob Fisher has been the program’s artistic constant.

“I think it could change,” he said, “but I hope after 12 years, it’s stable enough a thing that it won’t matter. It has its own momentum now.”

Mr. Fisher looks like a success. He is composed, relaxed. His clothes are crisp, unrumpled. His glasses are tinted. Still, there remains about him the earnest, green air of a high-school music geek, a man who is convinced he’s going to take a bad picture (“There are some with my eyes open?” he asks the photographer).

He also seems to be an extremely nice guy, or – at the very least – diplomatic. Asked to compare the experiences of collaborating with Mr. Bobbie, Ms. Marshall, and Mr. Viertel, he stopped dead. “Nobody’s ever asked me to do that before.” He paused. “What’s fit for print?” Apparently nothing, for he ended with, “I’ll try and get back to that question.” (We never did.)

The partnerships must have been good ones, nonetheless; he’s remained in touch with the two former directors. He was musical director and conductor of Ms. Marshall’s production of “Wonderful Town,” which began at Encores! and played on Broadway until last January. And with Mr. Bobbie, he followed the 1996 Encores! transfer of “Chicago,” which remains on Broadway and has become a dogged source of professional obligation for its supervising musical director.

“‘Chicago’ won’t die,” said Mr. Fisher, sounding like he might be okay with that demise should it happen. “I make a few trips to London each year. That production’s been running seven and a half years. We just turned 8 on Broadway. Some productions I say no to. South Africa is just starting up and I’m skipping that.” No trips to Cape Town for Mr. Fisher.

One aspect of “Chicago” he doesn’t have to worry about is replacing orchestra members. “Everywhere, it’s every player’s favorite job they’ve ever had. It’s a short show, they’re onstage, they get appreciated for what they do, and they get to look at women with hardly any clothes on.”

Rob Fisher, 52, was raised in Norfolk, Va., by two parents of North Carolina stock. His mother was a housewife, his father was a lifelong employee at the Norfolk Shipbuilding and Drydock Corp. who also possessed a gaggle of relatives who taught themselves to play various instruments by ear. “My older brother was taking piano lessons,” said Mr. Fisher, whose quarter century in New York has polished off his Southern accent. “So, when I was 6, I apparently demanded that I take piano lessons, too. He stopped a few years later, and I did not.”

Those people who don’t like musicals (there are some) and don’t live in New York (still more) may know Mr. Fisher best through his association with Garrison Keillor’s “A Prairie Home Companion” radio show, where he fronted the Coffee Club Orchestra for nearly five years. The name, which Mr. Fisher has retained for his ongoing ensemble, was Mr. Keillor’s creation. “We were on the subway going out to Brooklyn and Garrison said, out of the blue, ‘Maybe we should call it the Fisher Coffee Club Orchestra of the Air.’ I thought that was long.” It was shortened, though the name of Fisher still found radio fame as one of the show’s fake sponsors, Fisher Coffee. The fraudulent java purveyor’s martial theme song was played on the show every week:

Pour me a cup/
And fill it up/
With Fisher Coffee please./
Oh, what a brew/
It’s good for you/
And for your family.

Mr. Keillor’s decision to downsize the musical contingent of his show coincided with discussions Mr. Fisher began in 1992 with Ted Chapin and Judith Dakin about joining the newly conceived Encores!. “Judith Dakin was a fan of the Keillor show, and she wanted the Coffee Club Orchestra to have a presence at the City Center. She thought it would be the coolest thing.”

(He has since bought the name of the band from Mr. Keillor, who owned the trademark – “For a nominal fee,” Mr. Fisher hastened to add.)

Mr. Fisher’s final production with Encores! will be the May 12-16 presentation of Sheldon Harnick and Jerry Bock’s 1966 musical “The Apple Tree,” starring Kristin Chenoweth. “In picking a season, we usually try to pick an easy one, a medium one, and a hard one, in terms of restoration.” “The Apple Tree,” he said, was the easy one. “We found the full scores almost entirely. On a lot of those shows, after they closed on Broadway and went to a rental house, the score was simplified. They didn’t expect people to play as many instruments as they did on Broadway. The simplifications are sometimes hard to undo. And we want to present the show as it was first heard.”

And then he’ll be free to, perhaps, spend more time with a special someone? No. “I need a huge amount of time by myself and I travel a lot. So, I’m not a bargain for anybody.” Then, free to play what he likes best? Gershwin comes up on his resume an awful lot. What about him? “I do love George’s music and his and Ira’s songs a lot. I’m connected to whatever it is in their music that makes it them.” They’re his favorite writers, then? “No. See, that will change every day.” Only, this 24 hours, it actually is Gershwin. “Today I’m really wanting to play Gershwin’s ‘Concert in F’ again with an orchestra. I’ve played it a few times in my life. That was a very satisfying piece. I’d love to have another shot at it again. Print it!” Okay. All orchestras looking to employ an Encores!-free Rob Fisher: You read it here first.