Many of the pieces in "West Side Story" experiment with different melodic tricks. This song is notable for its prominent perfect fourth intervals, and a theme that starts on a pentatonic scale but develops into a western key.
Jenna Ushkowitz sang the song on Glee, on the episode Preggers. The song also was a plot device in the episode. When Tina (Ushkowitz) gets the part, Rachel (Lea Michele) says that she thought all West Side Story material goes to herself, also with both her and Natalie Wood being Jewish. At the end, when Tina still gets the song, Rachel quits Glee Club to star as Sally Bowles in the school production of Cabaret. Tonight was featured again in the fifth episode of the third season of the show, "The First Time," this time sung by Lea Michele and Darren Criss.