DICK MOTTA'S been on my mind a lot lately. And if you have to ask how come a star baseketball coach has been moving in on the music critic's territory, you have not been keeping in touch with the action lately.

So finally I called his house last Sunday to get a direct quote from the man who really knows what opera is about. But of course he was in Las Vegas. They were having NBA draft picks out there, the way opera companies do in Kansas City or Dallas or wherever they go to pick out the best new, young opera singers for the next couple of years.

What I wanted to do was to encourage Motta, now that that he's made World Champion with the phrase "The Opera's Not Over Till the fat Lady Sings," to go to greater heights.

You might think there aren't any, since the Bullets have already succeeded in educating the world that it must not move a muscle until Brunnhilde has sung her closing line - "Siegfried, Siegfried, sieh! Selig gruss dich dein Weib" - at the end of Wagner's "The Ring of the Nibelungen." Even though she takes 20 minutes to do it.

Ah, but you're wrong, and I am sure that if Motta had been home last Sunday he would have agreed instantly. I am sure that he had another winning phrase right on his lips - held in reserve in case it was needed. And I am sure, now that the Bullets have been victorious, he would not want us to hold it back:"Don't Clap Till the Music Stops."

All last week while Motta and the Bullets were preoccupied with flying out to Seattle and playing that final game on Wednesday, and then getting back to Dulles Airport, and the Capital Centre, and the White House, and RFK Stadium, the Metropolitan Opera was working out at Wolf Trap.

What was happening to the Met all week was sort of like what happened to the Sonics that Wednesday night. The Met singers and orchestra kept getting torpedoed when they least expected it, although from those they had thought were their friends!

For instance, one of the Met's star forwards - I mean top sopranos - Judith Blegen was singing Gilda in "Rigoletto." And she was was singing her big aria, "Caro nome" as few sopranos have sung it in recent years.

So what happens? She stops for a moment to take a breath so that she can go on with the next phrase, and a lot of people in the audience think that because the woman pauses for a moment, they should clap. So they do, and lots of others join in.

And suddenly, there is Blegen singing Gilda, with six gorgeous lines still to go, about to be joined by all the men in the chorus, and the whole orchestra still playing what Verdi wrote. And you can't hear a single note! Not a sound!See what I mean?

Things were even worse during Mozart's "Don Giovanni" the following Saturday, when Motta was getting ready for his picks in Las Vegas. The Metropolitan was pulling on one of the greatest operas in history. And every few minutes, just because some singer finished an aria, or a couple of them came to the end of a duet, there was this same widly enthusiastic burst of applause.

Let me show you: In the second act, Don Ottavio sings about his fiancee, Donna Anna, who is letting her grief over the murder of her father drive her around the bend. And Ottavio is hoping that she will get over the shock before it is too late. Naturally, he sings about all this. Here Is the end of his aria:

But notice that after his last syllable, "nar," which you can see there at the beginning of the next to the last line, Mozart gives the orchestra a beautiful kind of short epilogue. It probably lates about 30 seconds. You are supposed to listen to it before you start clapping. When those nine measures are over, there is a dead break, and everyone can carry on with the clapping as long as they like.

That's why i wanted to get hold of Motta on the phone. An opera fan who knows that, "The opera ain't over till the fat lady sings" also knows the truth of "Don't clap till the music stops!!!!!"

I just wanted him to be the one to say it.