Sometime in the early ’90s, Harry Nilsson walked into Warner Bros. with a new batch of demos. This is the man who hit No. 1 with the operatic pop of “Without You,” scored a Grammy with his cover of “Everybody’s Talkin’ ” — the theme for the Oscar-winning movie “Midnight Cowboy” — and was outed as John and Paul’s favorite artist before his 27th birthday.

Now he was 50, battling diabetes and heart disease, and it had been more than a decade since his last album. Mark Hudson, who had been working with Nilsson on these new songs, went to the meeting.

“And I begged Harry, ‘When I get in there, let me be Fred Astaire and do the tap dancing,’ ” Hudson says. “And Harry, he spoke his mind. We went in there and played them like three of the demos, and I could see it in their faces, and Harry goes, ‘You guys don’t get it, do you?’ I said, ‘Harry, music has changed a little bit.’ And he said, ‘Change this,’ and got up and walked out.”

Nilsson would be gone for good two years later, suffering a fatal heart attack on Jan. 15, 1994. And the demos would languish for decades, existing as rumors chatted about on fan sites or occasionally shared as bootlegs. But on Nov. 22, Omnivore Recordings will release “Losst and Founnd,” which features Nilsson’s final recordings with a production polish by Hudson and some of the late singer’s friends, including Van Dyke Parks, Jimmy Webb and drummer Jim Keltner. Kiefo Nilsson, who was 8 when his father died, added bass to the album.

“Losst and Founnd” is not Harry Nilsson’s greatest work, but it’s a fitting coda for one of music’s most original characters. When he emerged in the late ’60s, Nilsson had a gorgeous tenor that stretched across three and a half octaves, a wry sense of humor and a deep respect for the studio. He seemed capable of pulling off anything: a sublime tribute to his desk, an entire record of Randy Newman covers or standards performed with a full orchestra. His songs were often so cinematic in scope, it’s no wonder his catalogue became a favorite of film and television directors, whether punctuating drug paranoia in “Goodfellas” (“Jump Into the Fire”) or, earlier this year, the darkly comic reset in Natasha Lyonne’s “Russian Doll” (“Gotta Get Up”).

Though he never played live, Nilsson was once famous. John Lennon, in a late ’60s news conference, declared that “Nilsson’s my favorite group.” And it would be Lennon who produced Nilsson’s 1974 album “Pussy Cats,” during which the singer strained his voice to the point he was coughing up blood. “Pussy Cats” would be his last album to crack the Top 100. He put out his final studio album, “Flash Harry,” in 1980, but it was not even released in the United States.

Nilsson spent the last decade of his life recording an occasional song for a soundtrack, dabbling in film production and fighting for gun control. He had been crushed by Lennon’s death.

“I think he abandoned songs and thought they were trivial,” Parks says. “Then, all of a sudden, out of nowhere, he called me asking me to work. It was about 10:30 at night. I told him, ‘Harry, I won’t work late at night anymore.’ Then he worked surreptitiously with Mark on this album. He didn’t make any big pronouncements on it.”

Hudson, who would go on to co-write Aerosmith’s “Livin’ on the Edge” and produce Ringo Starr, started working with Nilsson in the 1980s.

In 1986, they recorded a demo of “Try.” They did “Losst and Founnd’s” title track on a four-track Tascam in 1987. Nilsson sang the vocals of “Hi-Heel Sneakers/Rescue Boy Medley” just two days before he died. Four other songs were recorded in Chicago in 1989, including what may be the emotional centerpiece of the new album, “U.C.L.A.,” a grooving ballad that manages to blend melancholy, hopefulness and, like the best of Nilsson’s writing, wit and wordplay. Who else rhymes “oyster bar” with “Ringo Starr”?

“The lyric is a tour de force in terms of pun,” Parks says. “The power of deception. The ultimate joy of each ball lobbed over the net that’s an incredible triumph of each thought because they’re all understandable inventions. And I’m absolutely delighted that it reveals his unerring falsetto.”

Nilsson family attorney Lee Blackman said that he and Una, the singer’s widow, had been trying to put out the Hudson tapes for years but could never work out the right deal. Then, he began talking to Omnivore, a boutique label that has released everything from the Beach Boys to Buck Owens and NRBQ in recent years. Brad Rosenberger, one of the company’s owners, was a huge fan and, in his previous job at Warner/Chappell publishing, had engineered deals to place Nilsson songs in such films as “Magnolia” and “You’ve Got Mail.” Rosenberger and Blackman then tracked down Hudson, who had one demand.

“I said, ‘I’m not going to let you put it out in the shape it’s in,’ ” Hudson says. “It just was Harry and I in the room with him chain-smoking and me playing every instrument. I said, ‘I’ll do it for nothing. I’ll do it in my studio. I’ll call all my friends.’ ”

Jimmy Webb came to play piano on the album closer, his “What Does a Woman See In a Man.” Nilsson sang it at a friend’s house one night in 1993. Only the vocal was salvaged. Keltner, whose first session with Nilsson had taken place 48 years ago on “Without You,” came in to add drums.

“And Mark said, ‘Do you have a favorite bass player?’ ” Keltner remembers.

Keltner had just met Kiefo Nilsson at a wedding and learned that he played bass.

“And he looked kind of like Harry,” Keltner says. “Tall and sandy-haired. I said, ‘Mark, you’ve got to call him.’ Thank goodness Mark is one of those guys who isn’t unbendable.”

Kiefo, 34, says he didn’t choke up during the recording. He played as he might at any session. He knows some fans may have grown attached to the bootlegged demos. But he was pleased when he and his mother, Una, sat and listened to the completed album in her living room this year.

“This is a good representation of what my dad was doing and where his artistry was at this point,” he says. “It’s never going to sound like a George Tipton record from the ’60s, but you still want to convey the sense of humor and wit and elegance to the songwriting. That’s what he leaves behind.”