Four men are sitting in front of two large windows; one man is playing a guitar, one is playing the bongo drums, and two are sitting back without instruments.
The four men are in front of windows.
"The four men are in front of windows." is a rephrasing of "Four men are sitting in front of two large windows; one man is playing a guitar, one is playing the bongo drums, and two are sitting back without instruments."
Both men are in front of windows.
Only two of four men in front of the window have instruments. The others are sitting with no guitar or bongo drums.