Michael Jackson’s voice coach heard him sing almost every day for years. One thing still amazed him.

“The first time I met Michael was at his house.”

That’s how Seth Riggs, the vocal coach who trained Michael Jackson’s voice for decades, remembers it. It was the early 1980s, and Quincy Jones, the producer behind “Thriller,” had asked him to work with the young star.

Getting in wasn’t simple. The front stairs at the house were being redone, so Seth went up and over the roof instead. When he knocked, Michael called him in. Seth found him in his room playing with his little pet monkey.

“Oh my God, what is this going to be?” Seth remembers thinking.

It turned into one of the longest partnerships in pop music. While Michael was making “Thriller,” the two of them reportedly worked together two hours a day, six days a week. Seth was there for “Bad” and “Dangerous” too. On the “Bad” world tour, he reportedly warmed Michael up three times a day, and Michael never missed a show.

Seth has coached a long list of famous singers over the years. But when people ask him about Michael, he doesn’t start with the high notes everyone knows from “Billie Jean” or “Thriller.” He talks about something most fans never heard.

Here’s Seth talking about the Michael he knew.

Michael’s voice coach remembers their years together

Seth describes Michael’s range as “enormous.” Up at the top, Michael could hit notes far above what most grown men can reach. That part, fans already know.

What surprised his coach was the other end. He called it “amazing.”

Michael rarely let anyone hear that side of his voice. On his records and on stage, he kept it light and high. In the room with his coach, during those daily warm-ups, it was a different story.

In 1994, a tape was rolling during one of their sessions. Here’s Michael with Seth, working through his scales.

Michael’s training session with his coach in 1994

So how low could Michael go? Seth said he could reach all the way down to a low C, a note you’d expect from a deep bass voice, and he could always hit the low E flat that a bass sings in Mozart’s opera “The Magic Flute.” At the top, he could go up to a G above high C.

Seth kept teaching for many more years and trained singers all over the world using the same method he used with Michael. He’s said the secret to keeping a big range is never forcing the voice. If you don’t push too hard for the high notes, he says, you never lose your bottom ones.