Memphis, Tennessee was only 90 miles west of Jackson, my childhood home. But Memphis was as far away as the north pole in my mind. The history that we were given about it was done in light pencil that hopscotched its way to a semi-solid landing with Elvis Presley on The Ed Sullivan Show. Sun Records considered itself the fuse that lit the 1950s with Elvis and rock'n'roll. With Carla and Rufus Thomas and Otis Redding, Stax Records brought blues to the hit parade with hooks and horns and a solid beat, evolving into Al Green and Willie Mitchell. Memphis meant music.

And unless you stop to think for a minute, you might forget that it was in Memphis that Dr Martin Luther King, Jr was shot and killed on a motel balcony on 4 April 1968. Stevie Wonder did not forget. In 1980, Stevie joined with the members of the Black Caucus in the US congress to speak out for the need to honour the day King was born, to make his birthday a national holiday.

The campaign began in earnest on Halloween of 1980 in Houston, Texas, with Stevie's national tour supporting a new LP called Hotter than July, featuring the song Happy Birthday, which advocated a holiday for King. I arrived in Houston in the early afternoon to join the tour as the opening act. By 15 January 1981, King's birthday, I had been working on the Hotter than July tour for 10 weeks.

What's amazing about people who are supposed to "think of everything" is how many things have never crossed their minds. That was never more clear to me than when I saw how things looked from the back of the outdoor stage set up on the Washington DC monument grounds as Stevie's rally for King got under way.

I would never claim to be the smartest son of a gun on the planet. But by the same token, by then I had been in this business for 10 years and had to feel as though I knew more than when I started. I had some new information crossing my mind as I climbed the back stairs on to the temporary stage and looked out at perhaps 50,000 people standing shoulder-to-shoulder across the expanse of the Mall, chanting: "Martin Luther King Day, we took a holiday!"

The Hotter than July tour was a project that, when taken as a whole, was set up to cover 16 weeks, or four months, a third of a year. The endeavour was cut into two six-week halves with a break – a rest period – that lasted a month. In essence, this rally was the half-time show before the second six-week half. One thing that knocked me out looking at this half-time show was how much I had not thought about. Like how much work was involved in organising a fucking rally. That was what Stevie had done and what had to have taken up so much of his offstage time when we were playing, and what must have consumed what I was calling a "rest period". The rally. Ways to publicise it, ways to dramatise it, ways to legitimise it.

Some of it was obvious. You had to have permits, such as a licence to have a parade. That seemed bizarre, but it took a necessary number of police to close certain streets or divert traffic or just stand around looking like police. And on the monument grounds there were wooden saw horses and security and crowd restraints and a stage and sound equipment and technicians to set it all up and run it. And I was enjoying another piece of equipment I felt was necessary: a heat-blowing machine to warm my chilly backside.

I had no idea what this was costing, what the total expenses were. Nor did I ever ask about it and have the expenses incurred by Stevie neurotically concealed from me. I didn't have any way to justify saying: "Hey, just what the hell is this gonna cost?" I considered that this information was probably something that was being distributed on a need-to-know basis, and apparently I did not have that. I didn't worry about why.

My respect for Stevie Wonder expanded in every direction that day. I was following his lead like a member of his band, because seeing as he had envisioned was a new level of believing. It was something that seeped in softly, and when you were personally touched by someone's effort and genuine sincerity, your brain said you didn't yet understand but your soul said you should trust.

The march in Washington on 15 Jan 1981 to publicise Martin Luther King Day. Photograph: Jonathan C Katzenellenbogen

We had been to Mayor Marion Barry's office earlier in the day. There, I was introduced to the winner of a citywide essay contest that had been run in the Washington DC school system. The theme of the essay was why King's birthday should be a national holiday, and the contest was open to middle-and high-school students.

A seventh grader [12 or 13-year-old] won, and I thought the fact that he was in the seventh grade was the headline out of that. After they introduced us, I took a few minutes to read his essay so I would know what to be listening for – my cue when he came to the end, because now, at the rally, I would present him to the crowd.

It was a grey winter day, the type of grey that looked permanent, not bothered with clouds or memories of blue. Grey, sullen, not threatening but sporting an attitude. When we got to the part of the programme where the kid was to read his essay, I introduced him and walked back offstage. I kept one ear on the loudspeakers because I had to be on it when he was through. That would be no more than five minutes, max.

At some stage, I heard the kid having trouble reading his own essay. I thought he might have been nervous with the big crowd and the TV audience – it must have felt as if everybody in the world was watching him. I could hear the crowd getting restless, and a couple of folks started giving the kid a hard time. Suddenly, mid-sentence, or maybe in the middle of a word, the kid stopped. He turned around and went back to his seat. It was a seat of honour, right behind the podium in the middle of the stage.

It was quiet now, just a sprinkle of sympathetic applause. I found my list of speakers and introduced the next one, but I realised something had gone wrong. As the next speaker approached the podium, I went over to the kid and said: "Let me see that essay there, brotherman." And sure enough, he had stopped at the top of his second page, a good five or six paragraphs from the end. He had been reading from a mimeographed copy of his essay, and the ink was faded – I would have needed night goggles or some shit to see what was on that paper.

I waited until that next speaker was through, then went up there and explained to the audience that I was going to introduce the kid again, and that he was going to read his essay to the end, and that they were going to listen. Yeah, I knew it was cold, I said, but it was cold for this kid, too, and he was reading from a faded copy, and I didn't want to hear nothing from the crowd but applause, period. "Have some patience with the young brother, please."

After I introduced him, I walked backstage again. He started to read again, and I heard him coming to the point where he had faltered, the part on the page that was damn near invisible. He started to falter again, and I listened for some wiseass to say something. But then it started to go smoothly, and I looked over and there was Diana Ross standing next to him with her arm around his shoulder. Without being in the way, without making it her essay, she helped him over those rough spots. My man's confidence got a lift and the crowd started to appreciate what he had written. I stood there thinking: there must be 30 or 40 adults up here on this stage, and she's the only one of us who thought to go up there and help the brother!

Gil Scott-Heron in 2010. Photograph: Anthony Barboza

Jesse Jackson spoke, too. His attitude was about changing the laws and about people needing to know more about Thurgood Marshall [the first African-American supreme court judge] and needing to know more about what happened, because the way to change America was through the law. You see, if you don't change the law, you don't change anything. You could burn your community down and somebody else would build it up; all you were doing was burning down some houses. But if you changed the law, then you had done a whole lot to change the foundation of society.

To be sure, I looked at the appearances there and then as a tribute of respect for King. But they were also an indication of respect for a brother for taking a step to bring a positive idea forward, to remind some of us that we could hardly criticise congressmen and other representatives for inaction if their attempts to push ideas important to us out in the open received no visible interest from those it purportedly would benefit most.

Yeah, this piece of legislation to make King's birthday into a national holiday looked like a long shot, especially with it being raised just after America had elected Ronald Reagan, who would be inaugurated at the other end of the Mall in five days. But if our community was to make valuable contributions, then those who made them had to be recognised as offering something of value. Why would the next one of us feel that he or she should make the effort, marshal the strength and somehow fortify him or herself against the opposition that always seemed stronger, if even a man who won the Nobel peace prize was ignored where those efforts for peace had done the most good?

All holidays should not be set aside for generals. To have the country honour men for doing what they did at a time when difficult personal decisions made their actions worthwhile for the overall good meant the same thing for all citizens. That had been both the point and the ultimate disappointment of what had once been called "the civil rights movement".

What was special about the 60s was that there was only one thing happening, one movement. And that was the civil rights movement. There were different organisations coming from different angles because of geography, but in essence everybody had the same objective. It came so suddenly, from so many different angles, things happening in so many different towns and cities at once, that the "powers that be" were caught off-guard.

Until the 60s, "the movement" had been the exclusive property of middle-aged and old people. Then it became a young people thing, and as the 60s opened up, the key word became "activism", with Stokely Carmichael and the SNCC [the Student Nonviolent Coordinating Committee], "freedom rides" [challenging segregation on interstate buses], and sit-ins. There was a new feeling of power in black communities. And once it got started, it was on the powers like paint.

But at some point a difference was created between "equality", "freedom" and "civil rights". Those differences were played up because something had to be done about the sudden unity among black folks all over the country. Folks got more media attention whenever they accentuated the differences. There were media-created splinters. Otherwise the civil rights movement would have been enough, and would have been more successful. Accomplishing the aims of the movement would have made "gay rights" and "women's rights" and "lefts and rights" extraneous.

But divide and conquer was the aim of programmes such as COINTELPRO [the FBI's covert attempt to infiltrate and disrupt groups deemed "subversive"]. And even though it ended up working damn near backward, it worked. They separated the fingers on the hand and gave each group a different demand; we lost our way. Separated, none of us seemed to know to watch out for COINTELPRO. J Edgar Hoover was dead, but in DC they honoured what he had said: fuck every one-a-them.

There I was at the halftime show, looking up and down the field, and I could see for the first time. I could see what this brother had seen long before, what really needed to be done.

We all took the stage. The crowd continued to chant: "Martin Luther King Day, we took a holiday!" Stevie stepped up to the mic and addressed them: "It's fitting," he said, "that we should gather here, for it was here that Martin Luther King inspired the entire nation and the world with his stirring words, his great vision both challenging and inspiring us with his great dream. People have asked, 'Why Stevie Wonder, as an artist?' Why should I be involved in this great cause? I'm Stevie Wonder the artist, yes, but I'm Steveland Morris, a man, a citizen of this country, and a human being. As an artist, my purpose is to communicate the message that can better improve the lives of all of us. I'd like to ask all of you just for one moment, if you will, to be silent and just to think and hear in your mind the voice of our Dr Martin Luther King ..."

Somehow, years later, it seems that Stevie's effort as the leader of this campaign has been forgotten. But it is something that we should all remember. Just as surely as we should remember 4 April 1968, we should celebrate 15 January. And we should not forget that Stevie remembered.

As Stevie sang on Happy Birthday:

We all know everything

That he stood for time will bring

For in peace our hearts will sing

Thanks to Martin Luther King Extracted from The Last Holiday: A Memoir by Gil Scott-Heron published by Canongate at £20. To order a copy for £16 with free UK p&p go to guardian.co.uk/bookshop or call 0330 333 6846. For more on Gil, including a short film of the last interview he did before he died and exclusive readings from The Last Holiday, go to www.canongate.tv