Musical theatre songs are often structured in very unique ways that fit the narrative or personality traits of the characters singing. The conventional verse-chorus song structure of pop songs has been used a lot but extra sections are often added to reflect the plot of the show.
In the last song of the first act, the various unresolved feelings of the characters are often emphasised so the audience can ponder over them in the interval as they use the toilet and eat their little tub of overpriced ice cream.
The last song of the first act in Les Miserables is "One Day More" and is musically structured with two sections of music, heard in this order: AABAABA.
Structurally we have:
An introduction
The A section sung by Valjean at 0'09 as he ponders over the secrets he is holding and the criminal life he is constantly running away from.
The A section sung by Marius at 0'24 but with a different melody reflecting how head-over-heels in love he is. He is joined in harmony by his lover who feels the same, Cosette.
The B section at 0'50 sung by Eponine who is heart-broken by the love she feels for Marius, which is not returned. We hear snippets of Marius and Cosette continuing their melodies simultaneously.
The A section is returned to at 1'19 with Enjorlas this time singing, rousing his political comrades who are about to stand up in the French revolution. Marius is wondering whether to join them or to pursue his love.
The A section is heard again after a key change at 1'46 by Javert, the police inspector pursuing Valjean, who is preparing to stand up against the revolutionaries. We also hear from Mr and Mrs Thenardier, who are willing to beg, borrow and steal anything to stay alive!
At 2'10 we hear the B section again, this time sung by the whole ensemble recalling the "Do You Hear The People Sing" leitmotif.
2'39 we hear all the melodies arranged polyphonically in the final A section, showing and juxtaposing the conflicting ambitions of the various characters.
As an end-of-act song, Defying Gravity also exposes the contrasting feelings of Elphaba, Glinda and the Ozians (ensemble). The structure can be viewed as verse-chorus form, particularly due to the fact that the chorus is climactic and recognisable as the main hook of the song.
The verses are based around similar chord progressions but the melodies are very different, again reflecting what the characters are feeling at that point in time.
Introduction - (beginning to 1'16/bar 33). This is stormy and argumentative as Elphaba and Glinda blame each other for the mess they are in. The word setting is what can be described as a recitative at the very start, meaning that the rhythms of the words sung reflect the rhythms of normal speech.
Verse 1 - (from 1'16/bar 34). This verse is sung by Elphaba who is hesitantly thinking about taking a stand. There is a determination behind it but she is also unsure and reticent.
Chorus - (from 1'49/bar 49). The distinctive chorus melody is catchy and heroic. Elphaba is now sure of herself.
Verse 2 - (from 2'04/bar 59). The verse chord progression is returned to again though with some development. It is more rhythmic and is sung by Glinda trying to stop Elphaba getting carried away and Elphaba herself feeling confident and self-assured about what she is doing.
Chorus - (from 2'36/bar 80).
Bridge - (from 2'48/bar 88). This is the "unlimited" section in which Elphaba tries to convince Glinda that they can use their magic for good. It is very mystical and intriguing. Glinda sings with her and is very tempted.
Chorus - (from 3'29/bar 103). The two characters sing together now. It seems Glinda is going to join her...
Underscore/transition - (from 3'41/bar 111). An underscore is a musical passage played underneath spoken dialogue. This is a very short section in which we suspect that Glinda is not going to stay with Elphaba.
Intro reprise - (from 3'53/bar 115). A reprise is when a song or section is brought back again. They are very common in musical theatre. Glinda sings as she did in the introduction but this time she is not angry but is accepting, calm and even supportive of Elphaba's decision.
Verse 3 - (from 4'32/bar 135). Again the same chords are heard but this verse includes a completely different melody again. Elphaba's higher vocal tessitura is heard and this is the point that we see her rise into the air with her broomstick, making it a particularly epic moment!
Chorus - (from 4'59/bar 152). The climax is prolonged for a final chorus.
Coda - (from 5'15/bar 162). The final section begins retrospectively and then the oppositional exclamations of Elphaba and the Ozians are heard.