( By Claudia Parsons )

NEW YORK, May 23 (Reuters) At 73, country music legend Willie Nelson is still doing headstands and smoking joints in the back of a tour bus at hundreds of concerts and, far from slowing down, he'd like to tour with the Rolling Stones.

''They like country music, we get along fine and Keith (Richards) is a good buddy of mine, so that would be good,'' Nelson said, adding that he's not much of a dancer compared to Stones front man Mick Jagger but he might give it a try.

''He keeps the microphone in his hand so he can walk around and kick -- I may try that next year,'' he said with a chuckle.

''We've talked about it for years and it just hasn't ever happened,'' Nelson said of a joint tour.

Meanwhile, fresh from two weeks of gigs in Canada, he's spreading a bit of Texas wisdom in a book called ''The Tao of Willie,'' co-authored with writer and actor Turk Pipkin, who describes the book as the result of 20 years of friendship.

Best known for such classic songs as ''Always on My Mind,'' ''On the Road Again'' and ''Crazy,'' Nelson has recorded 250 albums, written 2,500 songs and played live concerts for some 20 million people in a career spanning half a century.

The long-haired singer of ''Mammas Don't Let Your Babies Grow up to Be Cowboys'' raised some eyebrows earlier this year when he recorded a song about gay cowboys called ''Cowboys are Frequently Secretly (Fond of Each Other).'' Nelson said the book, published this month, came about more by accident than by design.

''Turk came up with the idea, and I said great,'' Nelson said in an interview. ''I wasn't lying in bed wondering, 'Oh I wish I could do the Tao.' I had to do a little research on the word myself to figure out how to say it and spell it.

''When I first saw it, it was the toe of Willie, so I thought 'Great, next year we'll do the finger.''' Don't worry if you don't know much about Tao, he writes, explaining that it is a philosophy of life based on a Chinese text called the Tao Te Ching, or ''The Way and Its Power.'' There are more jokes than heavy philosophy in the book, which is part memoir, part musing on lessons he has learned -- from picking cotton as a child in Texas, to failed marriages and falling foul of the tax man to the tune of million.

SONGS AND WIVES THAT GOT AWAY ''I'm sure I made a lot of mistakes,'' Nelson said with a smile, sitting in a luxury suite at New York's Carlyle Hotel, a whiff of marijuana drifting down the corridor.

Nelson admits he's had a few run-ins with the law over his pot smoking habits. ''If you're going to be out there with it, somebody's going to pull you over, just because they can. ... I talk about it a lot, but I'm not going to walk into some police station burning one down and say, 'How are you all doing?''' He says the pot smoking hasn't hindered his songwriting. On the contrary, it may have helped filter out the duds.

''I figured if it wasn't worth remembering it probably wasn't a very good song, so that would be the test, to see if I remembered it until I got back to a guitar or a piano,'' he said. ''That was usually a pretty good measuring stick, but I'm sure I forgot a few that might have been OK.'' For a man known in his youth for hard living and heavy drinking, Nelson, two decades into his fourth marriage, is in great shape. He earned his black belt at Tae Kwon Do at age 69, completing a spinning back-kick to break two boards as part of the test.

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