For a guy with a $5-million Broadway show riding on him, Peter Allen appears to be holding up well.

The Australian singer-dancer-songwriter seems unperturbed by early negative reactions to "Legs Diamond," a musical he has been working on since 1983. Its opening twice delayed by troubled previews, it is now scheduled to open next Monday."We know that this is a working situation," Allen said in an interview with Reuters during a rehearsal break at the Mark Hellinger Theater.

"We had 17 changes on Tuesday (Dec. 13)," some six weeks after previews began, he said. "I guess it's going great compared to three weeks ago. People can't believe it's the same show, but I guess that's what's supposed to happen."

Loosely based on the 1960 movie "The Rise and Fall of Legs Diamond," the splashy show tells the story of Jack Diamond (Allen), an ex-con infected with the showbiz bug. When he fails, he becomes a gangster, buys a speakeasy and fulfills his "gotta' dance, gotta' sing" yearnings.

Any resemblance between the character of Legs and Allen is purely intentional.

Allen, a Grammy and Oscar-winning songwriter ("I Honestly Love You," theme from "Arthur") helped spur a revival of New York's Radio City Music Hall when he took his flamboyant, high-energy concert hall act there in 1980, becoming the first outside performer ever to dance with the Rockettes.

Allen, 44, said he was looking for a change, but "Legs" provides him a tailor-made opportunity to be himself. "I have to play a character in this, but the audience comes to see me, and they want me to be me," he said.

Accordingly, the showman who has ridden camels onstage makes his "Legs" entrance descending on a giant electric sign. The "death" scene is staged with similar extravagance.

"It was the balance that was hard for me to get -- where the audience is still interested enough in the character after I step out of it."

Leaving Peter Allen completely behind, he said, "would be dangerous because the audience has been used to me chatting to them from the stage." It would probably also be unwise, since Allen has never acted before.

It's his audience, Allen says, that has been the key to the many changes made in the show, which include a new opening number and the deletion of two major characters.

"Your main aim in a musical is to please the audience," he said. "So what they like we leave in, and what they don't like we don't push on them, we take it out.

"But you can't try it out in rehearsal. The audience is the only thing."

Allen compared the "Legs" previews to the out-of-town tryouts that many big musicals undergo. In fact, the show was scheduled for a three-month run in Canada before a New York opening but that plan proved too costly.

"From the stories you hear, every show in the world was supposed to close out of town," he said. " `Fiddler on the Roof' they hated. Every place it went they said `Close this, it's terrible.' We just happen to be doing it in New York, in front of everybody."

Old movies help bolster his spirits, too. "I did see all those movies as a kid where the show opens and it's a terrible flop and they turn it around and make it into a hit," he said.

But he has learned, perhaps the hard way, one lesson about mounting a musical that the movies didn't prepare him for.

"It's probably the hardest thing to do in show business. If they would tell you at the beginning, you might not go through it."

Still the rumblings about the show just make Allen more determined. "It's like I just put the bit between my teeth and my nostrils flare and I go `OK, wait, just wait. I'll give you an American musical hit or else!"

Or else what? "Even if it closed opening night, it's been just a wonderful experience. It was exactly what I wanted to do. I mean I could sit in Trump Castle (a casino in Atlantic City, N.J.) singing `I Go to Rio' for gamblers, (but) how many years can I do that? I'd probably turn into Tom Jones or something."

Regardless of whether "Legs" dances its way to a gold mine or oblivion, the songman - discovered by Judy Garland in Hong Kong in 1964 - will keep on writing popular songs. He has to; he has a three-album contract with RCA to fulfill.

Beyond that, Allen says he's "never thought about the future."

While best known for light pop tunes like "I Go To Rio" and ballads on the order of the theme from "Arthur," Allen's songs often reflect and probe the phases of his life.

"I Could Really Show You Around" was a critical hit which contained the lyrics "I could sweep you up in a flash, I'll make you forget that you're short of cash, Think of all the parties we'll crash, With all the high class and all the trash . . . All you have to do is let me take you home."

Written in 1979, when drugs and discos were peaking in popularity, the song was said to reflect Allen's darker side. "Bi-Coastal" (1980) described a lifestyle more and more entertainers and jet-setters were living at the time.

"The Lives of Me" (1971) was said to have been inspired during a drug trip, which Allen confirms.

Nowadays, he accepts even a cup of coffee reluctantly, saying "it's not going to go well with my new vitamin regime."

It was just before "The Lives of Me" that Allen's much-publicized marriage to Garland's daughter, Liza Minelli, ended. Married in 1967, the couple became definitive scene-makers in New York, often popping up in avant-garde clubs like Max's Kansas City.

Allen became a headliner at clubs like the legendary Reno Sweeney's. He said that he broke a lot of rules when he did his act, but it's not so easy anymore.

"Please. After Prince and Madonna and Boy George, it's like, whaddya' gonna' do," he says.

As to the kind of songs inspired by the Reaganite '80s, Allen plays on his "I Could Really Show You Around."

"How about `I'd Like to Buy You A Cup of Tea,' " he asks.

Despite the wisecrack, Allen knows the damage that the '80s scourge AIDS has wrought on the theatrical community.

"It's just decimating it. You keep saying `We'll get so and so,' this costume designer or that book writer and it's `No, no, no, he's dead, he's dead.' It's just insane."

Allen has done countless AIDS benefits, and did so long before the cause became popular.

Whether at a benefit, in cabaret or on Broadway, Allen always seems to be having the time of his life.

"It's just real nice to be able to go out on a stage and everyone kind of likes you," he said.

"That's why in the first couple of weeks (in "Legs") when they didn't like me I thought `Gee, how weird. I don't know what's going on here.' "