David Harrington is in inspired mood, coming off the back of another concert celebrating the Kronos Quartet's 40th anniversary.

“We just had a concert in Paris, and it was a real high point for us, but it’s been pretty much nonstop this whole year,” he says. “We played in Los Angeles, San Francisco, then New York – the audiences have never been better. People are bringing their kids, and we have the university crowd and even younger. We are playing a lot of new pieces this year, and the audience have no idea what to expect. It doesn’t seem to matter: they are joining us on this exploration, which is what we are all about.”

The award-winning string quartet are renowned for their ability to reimagine and reinvent, something that was at the front of Harrington's mind when he founded Kronos in 1973. He did this after hearing the composer George Crumb's Black Angels, a shapeshifting work about the Vietnam War, featuring spoken word, and electronic effects; it chimed with his own curious nature.

"My parents were very supportive about it. They didn't play instruments, but we used to watch The Laurence Welk Show, and there was a really great violinist on it called Dick Kesner. There was something about the violin and the way he played it. Then a trio came to my school. I sat beside the violinist, and the tactility of it was so exciting, so I started playing it in fourth grade."

He joined the youth orchestra and spent more time in the record store near his high school than he did in class. “I got to explore so much music, from Africa, from everywhere, and I was listening to Bartók and Thelonius Monk.

“At age 14 the only string quartets I had ever played were by Haydn, Mozart, Beethoven and Schubert, but I had this pivotal moment where I realised that it was weird that these four guys all lived in the same city. When you look at a globe and see how many other cities and countries there are than Vienna and Austria, it’s inspiring.”

This openness radiates from Kronos, who have performed with everyone from The National and David Bowie to the film-maker Darren Aronofsky. (They worked on scores for Requiem for a Dream and Noah.)

“The performers and collaborators that join us are bringing their own tradition to our tradition, so someone like the pipa virtuoso Wu Man, from China, brings thousands of years of tradition and an incredible ability.”

This sense of positivity and collaboration is present in their Under 30 commissioning project, which was set up in 2003. Harrington, who says it is “one of the most important and satisfying things Kronos has ever been involved in”, describes the most recent work, by Mary Kouyoumdjian, as “astonishing”.

Tomorrow the group play their only Irish date this year, at Cork Opera House, in a concert featuring Brooklyn-based Julianna Barwick, whose folk-influenced and celestial compositions complement the atmosphere Kronos typically conjure.

Talk moves on to some of the quartet's longer-term collaborators, such as the composers Terry Riley and Philip Glass, and about Glass's concerns about persistent cuts in music education in the US.

“My daughter is a first-grade teacher in a San Francisco public school, and the opportunities that are available now are so different than when I was small,” says Harrington. “Individual teachers of great energy and merit find ways of circumventing the system. My daughter’s class of first-graders came to our rehearsal, and got to ask questions, and we played different aspects of the new pieces for them. The wealthiest country in the world is incredibly poor in so many ways.”

This is a dark turn for cultural policy to take, particularly as so many artists ask difficult questions of the conscience of nations.

“What you just said is one of the reasons why powerful people are trying to exclude the arts, and that is because people involved in music and literature and film and theatre, they ask the difficult questions. The arts community is attempting to make the world a better place, and there are a lot of forces attempting to make it a worse place.

“There is this struggle going on, and for powerful corporations and governments, frequently it is to their advantage to have an uneducated and unenlightened public, and music and theatre and literature are directly counter to that.”

Despite his concerns about the wider US, Harrington enthuses about the quartet’s home city, historically a beacon of US counter culture. “Walking down the street in San Francisco always inspires me. There is a tradition there of rethinking things and questioning. It is the perfect place for Kronos,” he says. “It is just the best time to be a musician right now that I can ever remember. We can be in touch with people from so many different backgrounds, different languages, different religions, and histories. For me the 40-year anniversary concerts are a launching point to the future. I don’t want to look back very far.”

The Kronos Quartet are at Cork Opera House, with support from Julianna Barwick, tomorrow