A CHAMBER quartet is a small ensemble of four musicians who perform classical music in an intimate setting. The term 'CHAMBER quartet' is derived from the word 'CHAMBER, ' which refers to a room or hall that is used for private performances. The most common instrumentation for a CHAMBER quartet is two violins, a viola, and a cello. The term 'walls' is a five-letter solution to the crossword clue for CHAMBER quartet, as walls are often found in the rooms or halls where CHAMBER quartets perform.