Asong on Willie Nelson's superb new album "Heroes," "No Place to Fly," was written by his son, Lukas Nelson, and it contains the lyric, "The road is like a river that sings when I'm alone/I'm sitting beside a window of light that floods in my eyes and keeps me from finding my way/And if I stayed home I'd only wish I was gone."

These are the words of a traveling musician, and the younger Nelson confirms that he wrote the lyrics to that song while crisscrossing the nation's highways - or, as his dad memorably put it, on the road again. "That was where my head was at," Nelson says. "I was on the road at the time, in an RV. Before then, we were on a bus. And before that, we were in a van. And I've enjoyed every minute of it."

Calling from New York after playing a New England show the previous night, Nelson seems in a good place. Raised on a tour bus - his father is one of the hardest-touring musicians of all time - Nelson has been playing with his crack collective Promise of the Real for more than three years, releasing two albums and an EP, the most recent being the stellar "Wasted," on which the band takes a quantum leap forward in both chemistry and confidence. The unifying spirit, Nelson says, comes from the lengthy time spent in cramped quarters together. "How could it not?" he asks rhetorically.

Wise beyond his 23 years, Nelson learned early on that the romantic image of touring life is a myth. "You're not always playing for 100,000 people or even for 100 people, especially as a young, struggling artist," he says. "The most important thing to learn is: Enjoy the struggle, every part of it."

Managed by Matt Charkow at POTR Music and booked by the Parallel 49 Agency, Nelson already knows what some artists never learn.

"There are two types of bands: the ones that get famous really quickly and then fade out, and the bands that get famous slowly and learn how to deal with the road," he says. "Learning how to live on the road is what helps you survive in the industry."

That's just where Nelson and Promise of the Real are now, touring a circuit of small clubs and large theaters and festivals of all sorts. Frequently, the smaller venues prove more beneficial than the larger halls.

"Even though sometimes we play for just 10 people, those 10 people enjoy the hell out of it," he says. "They become fans, and it builds slowly from there." One place that is slowly but surely building is Boston, where Nelson and Promise of the Real played Upstairs at the Middle East, a popular room that holds 200 patrons, the night before speaking to On the Road.

"We haven't been hitting the East Coast very hard, and not many people know us yet," he says. "Last night in Boston, only about 100 people saw us. But those 100 people had a great time." Far better markets for Nelson and Promise of the Real are Colorado, California, Utah and the Pacific Northwest, as well as his home state of Hawaii, where he pit stops about one month out of the year.

Sometimes it feels like an act is on the verge of getting more traction, which is the case with Nelson and Promise of the Real. But he admits it's difficult to notice any breakthrough in the midst of the current East Coast run.

"It's hard to see day to day, because we'll play some places and nobody will come," he says. "But I enjoy the struggle, and I'm not looking for anything except to be able to play another night somewhere and make a living."

Nelson recalls a salient quote from Eddie Vedder of Pearl Jam, a favorite band whose 2009 song "Just Breathe" was covered eloquently on "Heroes."

"Vedder said something on a video I saw, about how all these little dates you play give you the tools so when you do have success you don't implode," Nelson recalls. "I'm becoming closer with my band, and I have time to write a lot as we're riding down the road. I'm reading, I'm learning, I'm volunteering in Haiti next month. I'm living my life, I'm happy, and I'm already a success in my own eyes."••••