Lady Gaga knows what’s great. Which is why, when she sang that “Sound of Music” medley at the Oscars, she gave it her best Julie Andrews spin. “Wasn’t she terrific?” Andrews marvels. “She told me she rehearsed it in all my keys, and sang it [that way]. I said, ‘But they’re very high. Why would you do that?’ She said, ‘To honor you, I wanted to do it properly.’ ”

Indeed. “The Sound of Music” — the classic film made of Rodgers & Hammerstein’s musical about the singing nun-turned-stepmother of an Austrian sea captain’s brood — turned 50 this week. Amid the hoopla of TV specials and an anniversary-edition DVD/Blu-ray, its elegant, 79-year-old star gamely (if hoarsely) fielded questions. Dame Julie — she of the four-octave range, who lost her crystalline singing voice after a botched throat operation in 1997 — lives on Long Island these days, after years spent in LA with her late husband, film director Blake Edwards.

At a hotel suite the other day, perfectly coiffed and slender in a green leather jacket, the former Maria von Trapp and Mary Poppins — the role for which she won an Oscar, in 1965 — recalled “The Sound of Music,” the kissing prowess of co-star Christopher Plummer and more.

How many times have you seen the film?

Not as many as you think! Probably six, all the way through. I bump into it once in a while, either on the television or at some event. When I was introduced to my new stepchildren — Blake’s children — I arranged with [director] Robert Wise to do a screening just for them, and we had a picnic on the floor of the tiny little movie house I showed it in. It was a nice beginning.

How did your meeting go with the real Maria von Trapp?

She came on the set in Salzburg [in Austria]. She was very generous and said, “I’m very glad you’re playing [me] like a tomboy, because that’s the way I was.”

Plummer disdainfully referred to the film as “The Sound of Mucus” and “S&M.” Was he hard to work with?

I believe that, having done as much Shakespeare as he had, he [felt] a little out of his depth at being in a musical of such saccharine quality — he wasn’t sure whether he made the right choice. As the years have gone by, he’s reversed that opinion. He never once was difficult to work with. We really adored each other from Day 1 and have stayed friends ever since.

What were you two giggling about in that love scene?

We built the gazebo in Hollywood to light it properly, and they tipped these huge klieg lights downward to look like shafts of moonlight. Those lights had carbons in them that rubbed together, and being tipped that far over, the carbons began making terrible noises which seemed to comment on [our] performance. We had to stop and start . . . Finally we completely cracked up. Our director said, “Never mind. I’ll shoot you in silhouette.”

Was Christopher a good kisser?

Yes, oh yes. Indeed.

What did you think of the live version of “The Sound of Music” that aired recently on television? Was it really necessary?

I was able to catch a bit of it. Come on! Fifty years later, you can’t deny people the chance — everyone should have a crack at it. It’s an iconic piece. There should be other interpretations.

Yet no one has a voice like yours.

Thank you. I was given a wonderful education vocally by a fabulous lady who said, “Hang on to your words, Julie — that’s what’s going to pull you through!” And I always have. As much as I love the music, lyrics are the things that matter, because then you can tell a story.

And what are a few of your favorite things?

Oh God, easy, easy! Grandkids. My garden. My dogs. Home!