PROFESSIONAL COMEDY is tough. There are thousands of would-be comics, swallowing apples or appearing on the Gong Show, but few of these people have what it takes to become a successful comedian. First, you have to be funny; second, you have to be able to maintain your comic appeal for a long time--what good is a profession that you can pursue for only a few years? Although comedian Steve Martin may not be able to long maintain his frenetic style, he is now at the top of the profession. His fans emulate his manic delivery as well as his jokes, and Steve Martinisms are now popping up in conversations all the time. With the Martin delivery, an expression like "I'm a crazy kind of guy" can quickly become a byword.

Martin has enjoyed an incredible success on television. Martin, one of the most popular guest hosts on the Tonight Show, recently broke from the traditional routine of walking on to the stage to deliver his monologue. Instead, he drove out in a small sports car, raced across the stage to say hello to that night's stand-in for Ed McMahon and then drove back across the stage to greet the band.

Much of Martin's comedy relies on sight gags, which he pulls off very well. He may walk onto the stage and claim to be a professional comedian and then proceed to knock over the microphone. Or he may display his bunny ears or an arrow stuck through his head. At a concert earlier this year at Symphony Hall, Martin wanted to give his audience their money's worth and offered to show them "something you don't see every day." At that point he began to jump up and down and scream like a depraved lunatic.

You won't see something like that on Martin's first, and so far only, record, "Let's Get Small." That's the main drawback of the album, which is very funny in places. "Let's Get Small" was recorded live during a performance at the Boarding House in San Francisco. The effect of Martin knocking over his mike is just not the same on a record as it is when you see him do it. And the faces Martin makes as he plays the banjo are very hard to imagine when you're sitting in your living room listening to the record.

Still, there are many very clever bits on "Let's Get Small," despite the problems of sight gags that the listener can only imagine. Martin's voice is magnificent and many of his jokes work because of his ability to change his speech patterns so well.

Martin uses sight gags to start a successful routine. He tells the audience that he wants to play a song on his banjo (which he plays admirably on the record) and that he needs a blue spotlight for the number. The lighting crew at the back of the auditorium doesn't respond to his request. So Martin launches into a tirade about the hippie lighting crew that thinks it knows more about show business than Martin does, even though he's been in the business "for a few years, and I think I know what works best:"

I'm sorry, but I'm angry. I come out here and Ih-can't get a little cooperation from the backstage crew?

EXCUSE ME!

I'm sorry, I'm pissed.

Much of "Let's Get Small" is very funny, but He doesn't make fun of society directly but packs his stories with non sequiturs and relates incidents that could never happen. He begins the Grandmother's Song with an innocent verse that any matriarch would be proud to hear her offspring sing:

Be courteous, kind and forgiving,

Be gentle and peaceful each day,

Be warm and human and grateful,

And have a good thing to say.

But there is a marked deterioration in the song until the last verse, when Martin tells his audience: