The man who wrote some of the best pop songs ever tells Neil McCormick how he hooked up with the hip hop super-producer to make one of the most thrilling albums of his 50-year career

How can I put this delicately? Burt Bacharach doesn't look particularly bling. At 77, the easy listening legend's LA perma-tan skin is stretched tight, as thin and wrinkly as old parchment.

What is left of his silver hair is teased in an unkempt pile on top of his bony skull, and when he removes his sunglasses, his eyes are watery with age.

Sitting stiffly down at the table, he opens a travelling box filled with health supplements. "This is all that keeps me going these days," he jokes in a voice so hoarse and low it barely registers above a mumble.

Yet there is an undoubted energy and alertness about him as he turns to the business at hand, explaining how he came to collaborate with hip hop super-producer Dr Dre (the man behind Eminem and 50 Cent) on one of the most original and impressive albums of Bacharach's long career.

"I've always been into urban music," Bacharach whispers. "Aretha [Franklin], Gladys [Knight], Patti [LaBelle], that is a very comfortable place for me. I did an album two years ago with Ronnie Isley. It's not exactly straight-out rap, but it has the same roots."

Fans will probably be relieved to hear that Bacharach's album, At This Time (released by Sony/BMG next week) does not actually feature the great man rapping. "I wouldn't. I couldn't! I have a hard enough time singing," he confesses. "I'm very insecure about my voice. But what I have done is take the underpinnings of hip hop and written melody over it with conventional instruments. That's a real oboe playing, you know. That's a beautiful trumpet."

For a man who had his first number one almost 50 years ago, Bacharach retains a surprising sense of musical curiosity.

He met Dre in an LA studio. "He gave me some drum loops, bass patterns and said, 'Play with it, see what you come up with,' " Bacharach recalls. "It was a very interesting format for me structurally, to have the confinement of a four-bar loop. Harmonically, the challenge is thrown down - can you write a verse and chorus over the same four bars? Get those jagged strings, work over the bassline, there's a lot of polytonal, dissonant writing in there, it's passionate, it's got an energy."

Adding real drums and percussion and taking the pieces off on sometimes very lush, lateral melodic flights, Bacharach admits that he might have "strayed too far left for what Dre was visualising behind him while he raps", but, encouraged by Sony/BMG UK chairman Rob Stringer, Bacharach began to envisage an album of his own.

"Rob put up the challenge. He was saying, 'Do something different. Don't give me pop songs, which anyway they are not going to play on the radio.' "

Sometimes inclined to wander off on conversational tangents, for a moment Bacharach ruminates, almost to himself, on the changing face of pop. "I never thought the day would come," he mutters incredulously, "when Aretha was not guaranteed to be heard on the radio, when Gladys can't even get a deal. That's heartbreaking."

The outstanding melodicist whose classic songs with lyricist Hal David became part of the defining soundtrack of the '60s mulls briefly over his own reputation. "If I come up with a song, they always say it's not as good as I'll Never Fall in Love Again or Anyone Who Had a Heart."

At This Time should re-establish Bacharach as a true original. While reinterpreting contemporary forms with a classically melodic sensibility, he wilfully abandons the kind of formal pop structure that many would associate with him in search of something richer and stranger.

Crucially, in its mood of ruminative despair and disillusioned nostalgia, it is an album that could only have been made by a man of his advanced years, looking back regretfully on life, fearfully contemplating an uncertain future.

And it pulls no punches, railing at the powers that be, the deceitful politicians he judges chiefly responsible for the mess the world is in. It is, in essence, a political album, 21st-century protest songs from an easy living icon of the swinging '60s. And remarkably, for the first time, Bacharach has been moved to write lyrics himself.

"I always had good writers, and I left it with them. I took care of the orchestration and making the record. But I had some things to say; I'm getting more pissed off about what's going on in our country."

He says that he was never politically motivated, but the fallout from 9/11 belatedly politicised him. On Where Did It Go?, he eulogises the world that he grew up in, when it was safe to walk the streets. "I have a nine-year-old, a 12-year-old and a 19-year-old," he says. "I love them, and it's all wrapped up in my concern for the world. It's accentuated with my time in my life with these kids, young kids…" And for a moment, tears well up in his eyes. "You're not supposed to have young kids at my age."

The album might surprise some fans, but Bacharach is proud of it. "I'd say it's as good as anything I've ever written. Did I write cheery music? No. I never did. All my music is serious. I don't make ear candy."