Master Nelson, otherwise known as Willie, took his shoes off like everyone else before entering the Master Martial Arts studio in West Austin Monday. He was there to receive a fifth-degree black belt in Gongkwon Yusul, a relatively modern Korean martial art, and would henceforth be known by the title “Master.” Gongkwon Yusul is a mix of various techniques, heavy on striking, punching, kicking, and ground fighting. It is, says Master Sam Um, Willie’s teacher, a lot like Mixed Martial Arts, or MMA, the sport where men try to kill each other in cages. No one in Gongkwon Yusul tries to kill each other, though judging by Monday night’s exhibition, they do a lot of rough throwdowns and hard flips. They also fly through the air and break boards with their feet.

Willie, er, Master Nelson, has been coming to Um for twenty years. Nelson first approached him many years ago, with his wife, Annie, and young sons, Lucas and Micah, so they could learn Tae Kwon Do. “Martial arts build confidence,” Nelson said. “I wanted my kids to learn how to do these things. It’s good for you spiritually, mentally, and physically. There’s an inner calm that comes when you feel confidence that you can control any situation.” The Nelsons would come two or three times a week when he wasn’t on the road, and even then he would practice, doing his workouts in the aisles of his bus as it rolled down the highway. He would make videos of his progress in Tae Kwon Do and send them to Master Um, who would tell him he needed to work on his kicks or his blocks. Nelson did this with uncommon dedication and discipline, says Um, and eventually worked his way through two black belts in Tae Kwon Do, before moving on to Gongkwon Yusul, which is a rougher, more physical discipline. This is not a surprise—Nelson in his youth was a scrappy fighter, not the calm singer-songwriter we know today.

The small Master Martial Arts studio was packed Monday night—students in white Tae Kwon Do uniforms and black Gongkwon Yusul uniforms, family members, media, and onlookers. Nelson walked in and sat at a main table with Um, who welcomed the crowd. He called for demonstrations of Tae Kwon Do and Gongkwon Yusul. A petite five-year-old girl came forward, bowed to Nelson and Um—who both bowed in return—and did some of her Tae Kwon Do routine. Nelson looked on, a beatific smile on his face. Two men walked onto the mat, bowed, and gave a demonstration of the more physical aspects of Gongkwon Yusul—grappling, thrusting, throwing punches and blocking them, taking each other down, and rolling on the mat. At the end, they bowed and Nelson and Um bowed in return. The last exhibition featured three young men. While two of them held out wood boards at arm’s length, a third ran at them, yelling; he leaped into the air and turned mid-flight, breaking one board with his left foot and the other with his right. The crowd burst into applause. Nelson smiled and clapped too.

After the exhibition, Um awarded Nelson his certificate and the ceremony was over. But like a Willie concert, the show wasn’t over until Master Nelson left the room. And so, after each of the students paraded by him one by one, bowing, shaking hands, and posing for photos, Nelson took a page from his music performances: he signed autographs for twenty minutes—on uniforms, belts, T-shirts, cellphones, and guitars. He smiled and hugged. He posed for photos and kissed kids on the forehead. After the crowd sang him an early “Happy Birthday,” he took group photos with Um and the rest of the students.

Finally Nelson walked out in his bare feet and onto his bus, which was sitting in the parking lot. Once again he was Willie.

Sitting there, still in bare feet and black uniform, he talked about the black belt. “It’s probably as much honorary as anything,” he said, “for calling attention to the martial arts. I’m glad to call attention to Gongkwon Yusul and to Master Um.” But, he was asked, you did all the things those young folks did, right? You’ve broken boards with your feet? “Oh yeah. I’ve done all that. The higher the rank, the more you have to do.”

Though Um acknowledges that the belt was part honorary, he also says that Willie has done the training for it; at the ceremony Um had gone out of his way to extol Master Nelson’s dedication, passion, and most of all, stamina, telling how after a physically demanding class Willie invited Um to a show that night at the Backyard, after which the singer signed autographs for thirty minutes. “Then he had to party with his guests,” said Um. “So he has better stamina than I do.”

And he has high hopes for his oldest student. “I’m hoping he’ll be a Grand Master someday. If he keeps on training, keeps getting people involved, he would probably get his sixth-degree black belt in four or five years, then his seventh-degree by the time he turns ninety. He would be a Grand Master.”

Willie won’t rule it out. “I’m proud of his confidence in me,” he said, laughing. “I don’t think there’s a lot physically that I couldn’t do. It’s just a matter of staying alive long enough to do them. There’s always new stuff to learn—it’s like the guitar, there’s so much more to learn and you’re never gonna learn it all.”