Its elaborate ongoing project, which fuels the current tour, is titled Nomadak TX. As documented in an award-winning 2006 film and a 2009 CD, group founders Harkaitz Martinez and Igor Otxoa traveled to India, Mongolia, Saharan Africa and Scandinavia's Lapland region to collaborate with local musicians and vocalists. In each setting, they did their best to fashion a txalaparta from local materials, using stones when in the desert and even planks of ice in the Arctic north. The result is an explosion of global music, including but not limited to sitar, bouzouki, zither, strings, woodwinds, throat-singing and innumerable types of drum.

On tour, the ensemble includes Martinez and Mikel Ugarte on several types of txalaparta (the "tx" is pronounced like "ch"), along with Iñigo Egia on a world tour of percussion instruments and Mixel Ducau on sax, clarinet, guitar and alboka, a Basque wind instrument. 

In advance of the group's appearances Friday and Saturday at the Lotus Festival, Martinez was kind enough to answer a few questions via e-mail.

NUVO: Since the txalaparta almost disappeared at one point, is there a well-documented tradition of how to play it, or have you developed your approach independently?

In the '60s there were only two txalaparta player couples, each one formed by two brothers of two families, and they left us the way of playing they learned from their grandfathers. But after that there was a process in which the ones that learned from those old txalaparta players started to develop the instrument in a more musical way. We are from the next generation, and we developed the instrument to our way, but always respecting the way of sharing the rhythm between the two players.

NUVO: Why does it require two players?

For us, the txalaparta is not the physical instrument itself, it is the way of playing it, sharing the rhythm between two persons. That is why we don't understand the txalaparta without two players. It is its peculiarity, what makes it unique in the world.

NUVO: For the Nomadak project, why did you pick these four particular cultures to visit?

We chose them for different reasons. One was the level of nomadity that they had. From a non-nomadic people like the Adivasi people – the aborigines of India, that have always lived there – to the most nomadic people in the world, the Mongolian. In the middle there are the Sami people (of Lapland), that used to be nomads, but are not now generally. And the Berber and Saharawi people, many of them are nomads but with difficulties because of war and climate change that leave the oasis without water. Another reason was the music of those cultures. We were very interested in the Khoomei singing in Mongolia, and the Berber women's singing, and the Indian rhythms ...

NUVO: How did you meet the people and arrange the recordings?

Sometimes we made the arrangements before the travel, but other times we didn't contact any of them and it was just what we found on the trip. We think that, like in music, on the trips the improvisation is the most interesting, as you never know what you will find. So we had nice and unforgettable musical surprises on all the trips. We took with us a computer and a little studio, and usually an electricity generator, so we were autonomous to record in good quality wherever we went. Other times we had arranged meetings in studio.

NUVO: When you made a txalaparta from ice, were you pleased with the result?

That was one of the most marvelous moments of all the project. We never expected to do a txalaparta with ice, but we tried it, and it was so nice to work with the ice. If you cut too much you throw water on it and in few seconds it was frozen and the note was changed.

Oreka TX performs at Lotus Fest Sept. 17 and 18 at 10:30 p.m. at the Buskirk-Chumley Theatre and Sept. 18 at 12:35 p.m. for Lotus in the Park.

2009's Nomadak TX Live performance series incorporated projected footage from the 2006 documentary Nomadak TX: