This is a great piece for those of you who don't know it. It was written for solo english horn and trumpet with orchestra.
I think that the most beloved quality of this piece is that the title neatly and compactly describes the piece. Within seconds Copland has transported the audience to quiet city streets at night through his use of tone color in the opening F major chord.
The trumpet enters with a sixteenth note pattern that is suddenly kind of urgent and mysterious at the same time, a few measures later the english horn plays the same pattern as if communicating with the trumpet. The main theme of the piece is brought in by the english horn and then repeated by the trumpet, and they kind of variate off of it with a quarter note triplet figure.
I feel like the piece has three big sections which are marked by changing rhythms, the first one being the opening section with the sixteenth note patterns, the second one being the more lyric section (my favorite, and then another also lyric but melancholy sounding variation of that melody that seems to be trying to overcome a hardship. The sixteenth notes return towards the end of the piece and it seems like each of the three rhythmic patterns makes a return, the sixteenths, quarter note triplets, and quarter note melody all reappear. It seems like a rounded binary form, the middle does modulate to C minor, C major, Aflat major, then back to F major so it ends in the tonic key, witht the same basic idea as the beginning and a sense of repose like it was time to go to bed or something.