Having spent a fragment of a well-spent life playing trumpet in a band on Bourbon Street, New Orleans, the sound of a distant parade sets my hair crackling. The late Sir John Dankworth did much to bridge the rift between jazz and classical.

He said: ‘Beware purists; they mess everything up.’ Louis Armstrong growled in his gravelly voice: ‘There’s two sorts of music, man, good and bad.’ Thus to the dawn chorus, to which I hearken as I might a marching band many streets away, parading in old New Orleans on a sweltering afternoon. The lower-register instruments sound first, the pumping sousaphone and bass drum, and one by one the others fade in until, rounding the bend, you get the lot in full-blast stereo, each instrument individual, everyone ad-libbing, but the effect a harmonious whole. Like the marching band, the dawn chorus is a free show and, to hear it, choose a fine morning in late April or early May. Close to London, Epping Forest becomes a concert hall for one of the greatest musicals in Britain.

Wrap up warmly, take a folding chair and a flask of coffee, sit back, close your eyes and enjoy. Arrive in the pre-dawn hush, for some members of our band are early risers, and a lucky fan might catch the sweet trilling of the grasshopper warbler, nightingale or wood warbler warming up in the dark.

Standing on South Rampart Street, you half hear a distant sound: yes, there it is again, coming and going. You stop, cock your head and close your eyes. It’s the rhythmical bump of the sousaphone, that serpentine piece of musical plumbing invented, as a jazz wag told me, by famous brass-band composer John Phillip Phone. Back in the forest, it is the basso cooing of a woodpigeon, backed by the breathy trombone of a tawny owl sounding like a cow blowing across the top of a milk churn. The bass line laid down, there is an explosive burst of piccolo from a wren. For one of our smallest birds, its chirrups, whistles and trills are deafening at close range.

The clarinet fades in-George Lewis, perhaps, or Johnny Dodds-in the shape of a blackbird, shouting the odds from a beech, staking claim to his territory, his carolling making the woodland ring. He is one of the first to sing, unlike the song thrush, whose sweeter, more edgy song is preferred by many. She is a slugabed, however, not joining until the band has warmed up, although she sings later in the evening when the blackbird has put his instrument in its case. There comes a roll on the snare drum: a great spotted woodpecker hammers on a dead ash, a staccato machine-gun rattle. Then his cousin, the green woodpecker- or yaffle-swoops across the ride in undulating flight with a burst of maniacal laughter. These are minor punctuation marks on the score, irrelevant contributions from overenthusiastic spectators on the sidewalk, for, one by one, the serious musicians join in.

The robin is in full song now, unlike his fitful half-choruses of autumn and winter; he, too, is informing anyone with ears to hear that this is his patch and, Christmas-card bird or not, he knows how to scrap to defend it. Britain’s smallest bird, the goldcrest, has enjoyed a return, and you might hear his reedy treble weaving among the notes of his greater brethren.

The blackcap pipes, a jay blows his harsh kazoo, a chaffinch rings his tubular bell and, at last, the song thrush strikes up, the Louis Armstrong and leader of the band -soaring arpeggios, exuberant riffs and repeated phrases, ‘lest you think he never can recapture the first fine careless rapture’. He outplays the blackbird as in one of the cutting contests of the old jazzers when each tried to outdo the other, notes like icicles ringing along the balconies of the French Quarter. Hard to miss the ocarina of the cuckoo, as he should be here by now, although his numbers shrink every year-what a loss if he failed to arrive at all. What is summer without a cuckoo and a swallow?

Some band members grow as frail as those in Preservation Hall. Farmland birds-such as yellow hammer, willow warbler and corn bunting- decline, and the croo croo of the turtle dove is rare, its eggs preyed upon by our plague of magpies, squabs picked off by sparrowhawks. Ancient chroniclers told us all was well as long as ‘the voice of the turtle is heard in the land’. Its diminution bodes ill. If the song thrush is Armstrong, the nightingale is Bix Biederbecke, that sublime cornet player who died in his twenties before his genius had fully flowered. Like him, the nightingale is endangered, as muntjac have browsed the scrub that it and the willow warbler love. Bend down and you can peer from end to end of the wood, so degraded is the forest floor.

We round the bend and there is the band in full flow-in front, the leader capering with his decorated parasol just as a little egret, one of our newer birds, flies silent overhead. Some we lose, but we gain collared doves, once rare vagrants, now in every suburban garden, and egrets are here to stay, with Egyptian geese, cranes, goshawks and other European travellers moving north as-so we are told-climate change begins to bite.

Turn and watch as the band passes, amateur instrumentalists joining in, children dancing and all the infectious excitement that only New Orleans can engender. The parade passes, turns left into Basin Street, the music fades, one by one the instruments drift off, until at the end, you catch the last grunts of the sousa as it also dies away. Rise stiffly from your chair-it is full daylight. Take your empty flask and, with the band silent, save for the last woodpigeon cooing softly, uplifted and purged make your way back to the madness of the real world.