Several young girls, dressed in similar white and maroon outfits are playing their instruments while walking down the street.
There are several young girls dressed in similar outfits playing instruments.
"There are several young girls" is a rephrasing of "Several young girls are." "Dressed in similar outfits" is a less specific rephrasing of "dressed in similar white and maroon outfits." "Playing instruments" is a less specific rephrasing of "playing their instruments."
(-x)
(-x)