Jimmy Webb, Lyric Theatre, London

'Jimmy who?" Well, that's fair enough. I don't blame you. Everybody loves a great song. Not everybody can be bothered to read the surnames in the brackets. On his new album, Twilight of the Renegades, Jimmy Webb compares himself - not in so many words, but the inference is there for us to make - to Gauguin: a great artist unrecognised in his own lifetime.

'Jimmy who?" Well, that's fair enough. I don't blame you. Everybody loves a great song. Not everybody can be bothered to read the surnames in the brackets. On his new album, Twilight of the Renegades, Jimmy Webb compares himself - not in so many words, but the inference is there for us to make - to Gauguin: a great artist unrecognised in his own lifetime.

Webb, a son of a preacher man from rural Oklahoma, was a Sixties visionary whose forte was combining irresisitibly populist melodies - many of his compositions have become crooner or country standards - with often bizarre lyrics. I'd call him "Bacharach on acid", if that wasn't such a hackneyed construction. You may not know the name, but you'll know the songs.

The millions of dollars Webb must have made from songwriting for other artists must cushion the blow to his ego somewhat, but in recognition terms, Webb's stock is disgracefully low. But make no mistake: this man is a genius, a visionary, and in his own way, an out-and-out lunatic.

The first song he plays is "The Highwayman", a Grammy-winning country number which gives him a chance to spin some well-rehearsed yarns about "my good friend Willie Nelson", "my good friend Waylon Jennings" and "my good friend Johnny Cash". It's instantly clear why Webb never made it as a star in his own right: his wavering voice is plainly that, as Rosemary Clooney heard it, of "a damn songwriter". He makes up for it by being a stunningly dramatic pianist (Rachmaninov is said to be an inspiration). Halfway through "MacArthur Park", his playing becomes so intense that he throws off his jacket to free his arms.

Originally sung by Richard Harris, it allows him to wax lyrical about being taken by the legendary hellraiser to a "natural amphitheatre scooped out of the rock" on the west coast of Ireland, where the actor had "delivered his first Shakespearean soliloquy, with the waves for an audience".

"MacArthur Park" is Webb's craziest, most epic - and most-mocked - song, primarily known for its refrain: "Someone left the cake out in the rain/ I don't think that I can take it/ Cos it took so long to bake it/ And I'll never have that recipe again..." Legend has it that Webb actually saw a cake left out in the rain on a New York pavement. This is how he works: little vignettes, Polaroid snaps of real life, firing his imagination.

His most famous song, "Wichita Lineman", was inspired by the glimpse of an engineer up a telegraph pole. Webb invented a secret life for him, summarised in that devastating non sequitur: "And if it snows, that stretch down south will never stand the strain/ And I need you more than want you, and I want you for all time..." It's only rivalled by another Glen Campbell hit. "By The Time I Get To Phoenix" is a song of uncommon subtlety: is the protagonist having a callous laugh at the lover he leaves behind, or choking back remorse? I can never decide.

In the age of Linda Perry and Gregg Alexander, God knows we could use someone with Webb's eccentric commercialism. "The thing about war songs is," he says before "Galveston" with pointed irony, "they never go out of style." If only.

s.price@independent.co.uk