A few months after Frank Sinatra’s death in 1998, the comedian Alan King, speaking at a memorial dinner, remembered his friend as something more than a musician or an entertainer, but as an “event.” If anything, that’s an understatement.

Sinatra the “event” is well captured in “Sinatra Vegas,” a new boxed set released this week by Reprise Records containing five concerts on four CDs and one DVD. Las Vegas was the city that Sinatra, more than any other performer, transformed from a cow town to an entertainment capitol. As great a recording artist as he was, the full extent of Sinatra’s magic could only be fully appreciated live.

Yet Sinatra came very late to the live album party, and, in the entire LP era, only released two concert albums. Ella Fitzgerald, one of the singers he admired most and regarded as a peer, established herself as queen of the live album not long after the 12-inch longplay was perfected in the mid-’50s. She was quickly followed by Tony Bennett, Mel Torme, and Judy Garland; by the time Sinatra was ready to do a live album, he decided to wait until he could deliver a blockbuster. And he did exactly that in 1966, releasing, “Sinatra at the Sands,” a double album with Count Basie’s band taped at the Sands Hotel in Las Vegas. (Another concert, previously unreleased, from the same batch is included in the new box.)

As any Elvis Presley fan will tell you today, a big reason for the King’s unending posthumous success is the continuing flow of previously unreleased material to give the faithful something to listen to. “Vegas” is the first major Sinatra release in too many years, but it was worth the wait. The five shows included cover a quarter century of Sinatra time between 1961 and 1987. “Vegas” features 88 tracks, but its delights are numberless, and it reinforces what those of us who experienced Sinatra many times in concert remember — that, like a true jazz musician, he constantly played with his arrangements in performance. He never phrased a song exactly the same way twice, whether it was an up-tempo swinger or a slow love song.

“Vegas” offers a zillion examples of Sinatra’s spontaneous invention in action. He repeatedly references current events, and, on the two shows from the Sands (1961 and 1966), surrounded by gamblers, frequently alludes to a handful of Jacks: Sands majordomo Jack Entratter, Jack Daniels, and, at least once, President Kennedy. He also continually throws in irreverent ethnic epithets, singing in faux-Italian (a la Chico Marx), doing Amos ‘n’ Andy, or peppering his songs and speeches with off-color references to homosexuals and drug addicts. At the time, such remarks resided in the extreme margins of adults-only humor; today, they seem tamer than most of the cartoons on Comedy Central. Then too, there are complete surprises, like a torchy and largely unknown “saloon song” rendition of “Just One of Those Things” among many others, and a super-energized Basie-fied rendition of “Come Fly With Me.”

Most Sinatra fans will gravitate first to the two earliest concerts here, from the Sands in 1961, on which he displays the most sublimely perfect voice of any live recording, and ’66, which beautifully compliments to the famous Sands meeting with Basie that was issued 40 years ago.

Yet the three later shows — from 1978, ’82, and ’87 — are equally pricelesss, and should confirm that the Voice lost almost nothing as he evolved into Ol’ Blue Eyes and the Chairman of the Board.

The five concerts are heard more or less in their entirety, but the producers, working in conjunction with the Sinatra family, have made some interesting decisions. The only song that perhaps could have been left out — and never missed — is the 1966 live version of one of his signature anthems, “It Was a Very Good Year.” Attempting this with Basie was a mistake because the orchestration depends on arranger Gordon Jenkins’s symphonic-sized string section. Clarinetist Marshall Royal (who is verbally encouraged by Sinatra) and the singer both labor hard, but the stringless Basie band plays this chart about as well as the Berlin Philharmonic would play “Splanky.” Sinatra would certainly have been wiser to do it with just long-time accompanist Bill Miller, the same way he performs his amazingly moving but little known treatment of “Send In the Clowns” on the 1978 concert. But, morone! what the Basie band does with “Fly Me to the Moon!” Sinatra nails this signature swinger with more rocket-powered force and fury than any other performance I’ve ever heard.

The material omitted from the 1978 show — the one represented here on DVD — is of greater concern. In the middle of this concert, one of the few times Sinatra was actually filmed or videotaped in Sin City, the singer introduces several celebrities in the audience, Orson Welles (whom he calls a “genius,” and rightfully so) and the mayor of Los Angeles, Tom Bradley. He refers to Bradley as being “colored” — an aside that is mysteriously deleted from the DVD. I can’t imagine why it’s okay for Sinatra to poke fun at Jews and his fellow Italians, but not at blacks, especially since he literally kvells with delight that both Bradley and his wife are in the audience, and is obviously jazzed that Los Angeles now has a black mayor. He literally seems to be taking this fact as a personal point of pride.

The producers also snipped out Sinatra’s attacks on William Randolph Hearst and Louis B. Mayer, as well as a scathing Andrew Dice Clay-like appraisal of Elizabeth Taylor’s reproductive organs. On the unedited tape, Sinatra declaims, it turns out correctly: “I’m layin’ 11 to one that you don’t use this on television!”

“Vegas” also comes with a 60-page color booklet that amounts to a miniature photo album. It’s filled to the brim with visual ephemera galore from Sinatra’s Vegas days. There are tons of laudatory interview excerpts from various Sinatra insiders, including some of his rhythm section players. Producer Charles Pignone has provided helpful back-story on how these previously unissued recordings came to be made, although there is no analysis of the actual music on the discs, and none of the original arrangers are credited. The overall ambition, between the recordings and the memorabilia, is to transport the listener decades into the past, to when Sinatra ruled Las Vegas like Caesar ruled Rome. Do they succeed? Well, nothing could take the place of sitting front row at the Sands and experiencing the greatest interpreter of American popular song in the flesh, but these recordings come as close as anybody is ever going to come to actually being there.

wfriedwald@nysun.com