Sometimes the band plays in town.
There is a band of musicians in town. Each musician is contributes a different part to the music, and plays a different instrument (or maybe sings, etc).
A woman at the back goes crash on the cymbals.
One of the members of the band, who is sitting at the back, is responsible for playing the cymbals (maybe there's also a guy in front who's responsible for playing the saxophone, and a gal over on the left side who's on the piano).
Now, at one point during the performance, when the music calls for it, this musician, a woman, who sits at the back of the band and plays the cymbals, suddenly crashes them together, producing the loud, sharp sound characteristic of cymbals (which acts somewhat like "punctuation" in a musical piece).
And they always sparkle in the sun.
The cymbals, all made of brass, glimmer brightly as the sun shines on them.
The effect of the bright, varigated spots of light reflecting off the cymbals is reminiscent of their bright, sharp, reverberating sound.