In this number, all the participants talk about the eventful evening they feel is ahead, each with their own thoughts on what will happen.

There are three trains of thought:

1 Riff and Bernardo - thinking (in terms of their own gangs) of the fight arranged for later that evening

2 Anita - thinking about her 'nocturnal activities' with Bernardo after the fight

3 Tony and Maria - more romantic love, idealised, though Tony has to agree with Riff, in exasperation, to be present at the fight

Each group/individual states their case with their own line (Anita's is related to Riff/Bernardo but adapted) and then the different melodic lines are combined. This sort of idea has been used by many composers in different genres. Mozart's finales, for example, often have several characters singing similar music with similar rhyming words but with opposite meanings, or several different melodies altogether.

A fanfare-like figure starts the number. Immediately there is a feeling of unease created as there are strong hints towards bitonality. The bass ostinato is in E major while the accompaniment and ensuing melody are in the lydian mode.

Riff begins the taunting and posturing in a low range. Bernardo answers with a similar line. The range of the first two phrases is a tritone, the most important interval both melodically, harmonically, and symbolically in the whole piece.

The melody, sung by Riff and Bernardo in unison, has a blues scale feel to it with a flat 7th and a few blue notes. Each singer has the same words and music, possibly emphasising that, essentially, despite the differences in culture (American/Puerto Rican) the teenagers are in fact very similar in taste and outlook.

A slinky glissando on the saxophones announces the arrival of the alluring Anita. This sort of saxophone writing has been used in innumerable films and television programmes to signify a particularly alluring or sexy (usually female) character. Anita’s melody is similar to Riff and Bernardo’s, but swinging triplets in the vocal part emphasise her suggestive nature.

Anita's "Tonight" motif overlaps with Tony's "Tonight". The Latin American rhythms in the accompaniment are particularly strong and contrast with Tony's lyrical, long legato line. Riff sings alone, imploring Tony to support the Jets. Here the repetition of the word "Tonight" starts to show its true implications - that Tony may have to decide between seeing Maria and fighting her brother's gang.

Maria enters with a repetition of the balcony scene’s Tonight, but is accompanied by Riff singing a musical question and Tony answering with a rising semiquaver figure. Each line is adjusted

slightly to fit the new harmonies.

The Jets and Sharks sing along with their respective leaders using an augmented version of the "They began it" motif which incorporates a very obvious tritone, contrasting with the rest of the harmonically secure song.

The texture, though now quite complex, is never really more than 3 different parts. Maria and Tony sing in octaves, the Jets and Sharks are either in unison, singing alone or in homophonic harmony and Anita adds harmonising parts or snippets of earlier themes in a highly suggestive manner (her final line is actually the same text as that sung by both gangs but her context is, of course, much different).

The rhythmic habanera accompaniment continues in the orchestra but the vocal parts become increasingly polyphonic. The number ends with a massive perfect cadence with Maria soaring up

to a top C.

Tonight is particularly significant to West Side Story because…

The lyrics, characterisation, and music are all perfectly balanced and integrated. Each character's music reflects their thoughts and hopes, whether the very simple, snappy delivery of the gang leaders, the romantic yearning of Maria and Tony or Anita's sultry and unsubtle leering.

The significance of the evening's events will be life-shattering, so the constant use of the word "tonight" and the "Tonight" motif is particularly thought-provoking.

Using a conventional operatic technique (different characters on stage saying the same or different lines at the same time but giving it their own personal context), plus the clever use of polyphony in the vocal writing - is one of the things which sets West Side Story apart from many musicals