His black hair may be turning grey but his voice is still as deep as the mine shafts he sings about and still as pure as the sweat from his working man's chest. Because Gil Scott Heron is growing old with honour.

He casually walks onto stage, dressed in jeans and a t-shirt and is sitting down on an upturned flight case behind his piano before most of realise that it's him. He smiles. "How's about everybody? How's it going?" Then he begins, looping a rhythm on his piano and singing: "There's a war going on/We're under attack/We're fighting back/Fighting back/Fighting back." It's not sung with rage, nor anger, nor bitterness. No, it's a calm, earthy melody, like a gospel tune. And it takes its time because what it represents is not a people lashing out with blind fury but rather a people prepared for the long road.

Some distance on, the bongos and reggae-style drums join in, then comes the bass and drums, then guitar, then piano. The sound deepens rather than builds and it doesn't really finish because the melody, rhythm and message work their way into our consciousness: "There's a war going on/We're under attack/We're fighting back/Fighting back/Fighting back."

Gil Scott Heron and his band understand that oppression must be addressed but that what the oppressed need most of all are reasons to celebrate. The music we heard tonight was most definitely celebratory. He celebrated his uncle who worked for twenty seven years in a coal mine and he celebrated the resistance to the all-year-long, all-decade-long, 'Winter In America'. The band celebrated. The bass, guitar and drums were so good in their technical and spiritual reach that they left us gasping, stunned and feeling that we had experienced magic. And the songs were not so much songs as histories, journeys. They trekked out and never really ended.

Two hours later, the aisles were full and the seats empty and everybody was up dancing. And that was the real triumph of tonight. For all the troubles that Gil Scott Heron has lived through, he has never lost his belief in a better tomorrow. Nor has he lost the love of the entertainer. He came back to us for an encore, as happy to be with us as we were to be with him. "They tell me I'm breaking the curfew. Well, I'm going to pay for this one. This song is on me."

Grey-haired he may be but Gil Scott Heron and his magnificent band took soul and funk, jazz and reggae and brought them to a spiritual high, leaving us all born again in music. Fighting back never sounded so good: I can only hope that he'll remember us and come back.

• Gerry McGovern