Complex sentence: Unable to make too much noise, they focused on their vocals and played mainly acoustic instruments, describing their music as "pop de chambre" due to its similarities with chamber music ("musique de chamber" in French).
Split into simpler sentences: Unable to make too much noise, they worked on their voices and played mainly on acoustic instruments. They described themselves as "pop de chambre" to describe their music's similarity with chamber music ("musique de chamber" in French).