For the second LEM concert held in Macba’s chilly auditorium, last night, ZNGR Electroacoustic Ensemble: Carlos Zingaro (in the middle) flanked by an equally serious Emidio Buchino (right) and Carlos Santos (left), met with a smattering of souls and an awestruck silence. A classically-trained violinist, Portuguese Zingaro is a LEM pioneer, having worked with the festival from the beginning. His musical style is to reveal, while also letting us know that he’s keeping things from us: the slides of his violin suppressed, as if netted by a crochet of electronica that carried it up there to linger with the air conditioning. It was less melancholic than soothing, little surprise sounds gleamed, instantly logical, and whatever Buchino was doing with his guitar or Santos was concentrating on didn’t matter. There was barely an acknowledgment between them throughout, nor between them and the audience at the end when, despite persistent applause, they filed gravely into the back room and didn’t reappear, even when somebody whistled.