Richard Marx was friends with the late-Olivia Newton-John for four decades.

While she’s known for her talent, Marx said the “Grease” star’s humanity was “the most extraordinary thing about her.”

“On my 20th birthday, I had only met Olivia maybe six months before that, she surprised me and took me to a birthday dinner for my 20th birthday to Le Dome,” he explained. “We ended up singing, making records together, performing together, we were just dear friends.”

Newton-John passed away Monday at 73.

“She was such a fighter, and she’s made such a difference in the world, and she’s one of the only few famous people I can think of who was truly universally loved,” Marx explained. “There was no one who was like, ‘nah, I don’t really like her.’ Everybody loved her.”

The singer, songwriter and producer went on to explain more about the “Physical” singer’s vocal prowess.

“Olivia was a phenomenal singer,” he said. “She could sing harder, pop-rock stuff, and she could sing ‘I Honestly Love You’ in the next breath.”

Marx is taking his own voice on the road. In two weeks, he kicks off his European tour in Spain.

“It’s like the most expensive European tour I’ve done in a long time,” he said. “I can’t wait.”

While Marx has a new album coming out in September, he guarantees fans he’ll be playing the songs they want to hear on this tour.

“I only do a couple of new songs in my show traditionally, because I go to concerts too, and I know how I feel if the band comes out or the artist comes out and goes ‘okay, now we’re going to do a bunch of songs from the new album’ that’s when I’m going to go get popcorn,” he joked. “So, I scatter a couple of new songs throughout my show, but it’s a greatest hits show.”

His new album “Songwriter” contains 20 songs that are a combination of pop, rock, country and slow ballads.

You can get Marx’s new album on Sept. 30. His new single, co-written with Keith Urban, drops Aug. 12 wherever you get your music.