"Here come the Jets like a bat out of hell..."

Bernstein plays with the rhythms and beats in West Side Story quite a bit.  Its almost as if the ear hears something very different than the sheet music has written on it.  The strongest case of this, at least to me, is "Jet Song".  Here is a sample of the sheet music:

At the beginning of the song we are told that the piece is in 6/8 meter.  Both parts in the piano reflect that time signature correctly.  The base line keeps a strong pulse on beats 1 and 4 throughout the entire piece and the treble line, although mainly made up of syncopations, is still accurately written in 6/8.  However, take a look at the melody line that the character Riff sings.  The line is still in the meter 6/8 but it is annotated as if it were in 3/4 with three quarter notes. If the same line were correctly annotated in 6/8 it would be a quarter note followed by two eighth notes tied together followed by another quarter note.  However Bernstein does not do this.  The two time signatures are drastically different.  While the downbeats for 6/8 are on 1 and 4, the downbeats in 3/4 are on 1, 3, and 5.  When both of the lines come together, it doesn't sound much like 6/8 or 3/4.  Instead it has the feeling of being in 4/4 or 2/4 with the piano treble line having a bit of a swing rhythm and the vocal line also having a swing feel all in triplets. Here is an example (starts around 0:21):

So as you can hear, it does sound more like 2/4 or 4/4 with a swing.  But since it is written in 6/8, the swing is actually annotated for us.  Playing what is written on the page with exact precision will give us the swing feel without having to add anything else.