(CNN) It was a night to remember: 1.3 million people crammed in city parks and pavements, blocking highways and craning their necks for a glimpse of the largest concert the world had ever seen, all in celebration of NASA.

On April 5, 1986, electronic music composer Jean-Michel Jarre led an event of riotous spectacle, lighting up the Houston skyline with lasers, vast projections and fireworks, blasting out synthesizer sounds into the night air. But someone was missing.

The concert had been due to climax with something totally unique. A young African-American astronaut named Ron McNair was to have performed part of the concert from miles above the city, inside the space shuttle Challenger.

The astronaut and his saxophone

The talented saxophonist had worked with Jarre to compose a special piece that was meant to link Earth and space for a moment of joyous celebration; but the piece and the concert instead took on a totally different meaning.

McNair was as passionate about music as he was about space travel.

Grammy-winning jazz musician Kirk Whalum recalls their first meeting: "I was playing at a club in Houston called Cody's, and Ron would come in, with these big thick spectacles, you know, the nerdiest of the nerds, and he said, 'I play saxophone,' I said, 'Hey great, tell me about it', and he said, 'Yeah, I'm an astronaut,' and I was like, wow, OK!"

Whalum laughs when he describes their second encounter. "So the next time he came in, being a good host I was supposed to remember something about him, and I said, 'OK now, I know I was supposed to remember something about you, I know you play saxophone, are you a flight attendant?'"

He remembers his horror when he realized his mistake. "I just wanted to jump out of the window!"

A call from NASA

Jarre, the multiplatinum-selling electronic music pioneer who is name-checked by science fiction author Arthur C Clarke in the notes of "2010: Odyssey Two," had been approached by NASA to perform a special concert in Houston.

The Frenchman -- currently preparing for a world tour with his new "Electronica" project -- vividly remembers his first visit to the organization's headquarters. "My first meeting in NASA was absolutely surreal. All these astronauts sitting in their offices, working on their stuff. We had our first meeting with lots of astronauts around the table."

During these early meetings Jarre was told about McNair's talent. "We had this idea that this astronaut could play live, in the weightlessness of space, during the concert, because a new shuttle was going to be launched weeks before."

Jarre and McNair hit it off instantly. "We met with Ron, who was part of the early discussions, and we got along very well together, and his family as well. They were absolutely charming people," he remembers.

"Ron was first of all a fantastic human being, and like a lot of astronauts, he was a humanist, in a very modern sense of the word. Also -- like all astronauts -- he was a dreamer."

Working together was not without problems, however. In the months leading up to the event Jarre was busily composing "Rendez-Vous," the new album that would form the Houston concert's backbone. Working in London and Paris during the week, he traveled to Texas every weekend.

Playing in space

McNair, meanwhile, was balancing the extreme demands of his role as an astronaut with his role at the concert. "It was a lot of pressure for both sides," Jarre tells CNN.

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"For him, having to learn a special piece of music, and playing this in the weightlessness of space, with all the technical problems, like saliva, how to eliminate saliva in space, all these kinds of things, and also on my side, writing a piece of music for an astronaut was something by its essence quite challenging."

Jarre also came up with an idea for the track that, unbeknown to him, would take on a whole new meaning at the concert itself.

"I found out from talking to people that in the total silence of space what you can hear the most is your own heartbeat. And then I got the idea to use Ron's heartbeat to create the loop and the beat of the track. Obviously now, looking back, it has such a meaning given what happened later on."

In the weeks leading up to the launch, McNair joined his fellow astronauts in quarantine, making contact with Jarre more difficult. In a world before mobile phones, they devised a neat plan: "Ron told me, 'We can talk every day at 2 o'clock precisely, because I will go through a corridor where there is a public telephone, and I'll give you this number, and you can ring me at this moment'."

Launch day, and tragedy

Then came the day of the launch. McNair called Jarre one final time. "We talked in the morning, and he said 'OK, this is D-day'," Jarre recalls sadly. "We're going to lift off this afternoon, so you can watch us launch on TV, and I'll see you in a few weeks."

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Over in Houston, Whalum had played at a gig the previous evening. "That morning, my wife and my little baby -- who's now 30 -- were there with the TV on," he told CNN. "I was still asleep from playing late, my wife came and woke me and said 'come look'."

At launch, Challenger soared into the sky above Cape Canaveral's famous Kennedy Space Center.

Seventy-three seconds later, a seal on one of its rocket boosters failed. The failure was catastrophic. The shuttle's giant fuel tank exploded. As the world watched in horror, Challenger's seven crew members, including Ron McNair, were killed.

Jarre was in his Paris recording studio. "We were quite a group of people, families and also the musicians involved. We stopped the rehearsal because we wanted to share this fantastic moment all together, with Ron, and with all of them," he explained.

Tears and despair

Their excitement quickly turned to despair. "We were all in tears, and I just wanted to just stop and just abandon the project, because I said this is nonsense, this concert has no sense now.

"I was obviously affected, and really sad for my friend, because through all this we became really good friends with Ron and I was so shocked by just the loss of a friend."

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Whalum's voice pauses and falters with emotion describing the moment. "It's funny, it still affects me. I mean, that was really something."

The idea of the concert, conceived so closely with Challenger and NASA, now felt absurd to Jarre: "Suddenly all this just killed me, and I had no more energy. I said, 'just forget it.'"

But almost immediately, the calls came urging him to continue.

Carrying on

"Lots of different astronauts called me, different people from NASA, people like (astronaut) Bruce McCandless, who was a friend of Ron's, and said 'you have to carry on', there is no way that this concert cannot happen, because it has to be a tribute to the astronauts, it has to pay tribute to these modern heroes."

The musicians and organizers regrouped. The first issue concerned McNair's piece. Who could possibly take his place? His friend Whalum was the obvious choice.

"Ron's wife, Cheryl, called me weeks later and said, 'Would you perform this piece, which had been written for Ron to perform, in his stead at the event?' I was just blown away, I mean I was just 24 years old, I was so honored."

On the day of the concert itself, downtown Houston was a frenzy of activity. With hours to go, the city's freeways were either closed or completely gridlocked as well over a million people made their way to watch.

Gridlock in Houston

Whalum was traveling to the gig. "A lot of freeways were closed. People were sitting on the freeway. Getting there was madness, we were riding in the feeder lane, bumping along by the side of the road trying to get there; I mean, I barely made it."

Spotlights illuminate the Houston skyline during Jean-Michel Jarre's April 1986 concert.

Jarre recalls seeing the scenes on TV: "I looked at the pictures of cars jamming the roads, and suddenly realized they were all empty!" Jarre laughs. "People were sitting on top of them, listening to their radios or ghetto blasters!"

"At sunset we went to the window and looked down to see a sort of dark ink, like a pot of ink had been put on the green of the field below," Jarre remembers. "We thought it was a reflection of the sunset, but then suddenly realized it was the crowd, and the crowd was actually everywhere!

"It was such a shock, I mean it was beyond being scared of going on stage. It was like being part of a community sharing this moment. It gave me a real positive energy to go on stage, I mean otherwise this kind of vision can scare anyone!"

On stage, a tower had been constructed for Whalum to stand on and play McNair's part. "Going on stage took on a new meaning that day," he remembers. "Because not to mention this horde, this mass of humanity, and all the security just to get to this spot, but then they had to hoist my instrument up, and then I was climbing up this crazy ladder to get to the top of this scaffold."

'Ron's Piece'

When the moment came to play the track -- "Last Rendez Vous," or "Ron's Piece," as it became known, Whalum's performance was searing.

"The way Kirk played this piece was absolutely amazing," Jarre says. "He added something more. He was playing the piece, but he was also playing for Ron, and his version is my favorite version."

Fireworks explode off Houston's skyscrapers during Jean-Michel Jarre's record-breaking show.

Whalum vividly remembers the sound of his soprano saxophone piercing the waves of electronic music.

"To have that lonely voice of something analogue, with a reed on it, soaring through -- especially with the range of the soprano -- cutting through all these analogue synths, which were very layered and atmospheric, was quite 'other-worldly'."

Against all the odds, the concert was an unqualified success. At the time it was the largest ever audience for such an event. Houston was alive with a spectacle the likes of which the world had never seen.

A unifying moment

It was also a remarkable moment for a deeply wounded city. "I think this project actually created, I hope, and I felt, a slight soothing effect," Jarre says. "It was like time was stopping for a while, and suddenly everybody was around the astronauts, around NASA, and paying tribute to these people."

Whalum recalls a special feeling. "There's an aspect of it that I treasure," he says.

"You know, this is Texas, and America's original sin is ever present with us when we wake up every morning, you know, you wake up as a black person. All of those things faded away, you know? The Muslim, the Christian, the Jew, I mean everybody felt like proud Texans and proud Americans at that moment, and music did that.

"People still don't understand how vitally important music is in moments like that, to bring people together and think along the lines of being one, of being fragile. It was a unifying moment."