One example might be “Agony” in Sondheim’s Into the Woods, though it’s somewhat iffy. The first time the two Princes Charming sing about their “love” of Cinderella and Rapunzel, the song is light, romantic, and ever-so-slightly disturbing if you’re paying attention. The music doesn’t change in the reprise, but the lyrics do–enough to make inescapable what is only implied in the first song: that both Princes are vain, selfish, untrustworthy jackasses.
Precisely. When first she sings it, Tara thinks she is being metaphorical; the reprise makes it clear that she is, in fact, in a borderline abusive relationship.
“All I Ask of You” from Phantom of the Opera. Goes from Raul and Christine talking about loving each other (“Love me, that’s all I ask of you”) to the Phantom threatening her for shunning him (“you will curse the day you did not do, what the phantom asked of you”).
For that matter, Aldonza’s song (I was born in a ditch to a mother who left me there…) is basically the same tune as Man of La Mancha, but much more detailed and ornate. It’s like it’s emphasizing that Quixote’s world is a mere fantasy, compared with Aldonza’s reality.
The latter point is noted —I see that he was looking for examples, not opinions. That said, it is extraordinarily common. Offhand, I can’t think of a single Webber musical that doesn’t have at least a few seconds of it. And actually… I can’t think of a single musical I’ve watched that doesn’t have it. And I’m far from a musicals-junkie, but you still see quite a few over time.
(ETA: the cliché is definitely wistful and/or sad — Joseph and the Amazing Technicolor Dream Coat/“Any Dream Will Do”, Evita/“Another Suitcase”, etc. Opening it up to other moods makes it a bit wider, I suppose.)
It doesn’t only happen in musicals, but also in quite a few movies and shows where the music features a little more prominently as part of the storytelling rather than just serving to set the mood in the background (Did that make sense? Did that sound pretentious? I’ll move on.)
An example that comes to mind soundtrack-wise is Casino Royale. All through the movie’s score, they play the Casino Royale theme as a lietmotif for when Bond is up to something or preparing for some task (such as when he’s first putting on the dinner jacket that Vesper has given him). If you listen close to the tune, you can also hear the James Bond string lietmotif just sorta plucking its way along in melody with the Casino Royale theme. It’s not until the very end of the movie that the CR theme gets dropped entirely, and we’re treated to the James Bond theme itself as he gives his trademark introduction (while carrying a submachine gun, no less)
And yeah, Once More With Feeling (AKA “The Buffy Musical”) has a couple of great reprises. Other than “Under Your Spell” (which, if you like to partake in fanwanking, you can suppose that Willow never sings in that song because she’s feeling guilty about what she’s done to Tara, rather than Alyson Hanningan merely being stage-shy about her singing voice).
Another reprise from OMWF is “Coda”, which reprises “Rest In Peace” and “Walk Through The Fire”. In the original songs, Spike is singing about how Buffy won’t reciprocate his feelings, and yet she won’t leave him alone either, while Buffy is singing about how, after being pulled from Heaven, she can’t feel anything on Earth, just a state of emotional disconnect. In the reprise, both of their songs come together to show that they have complimentary needs. Spike can get the affection he craves from Buffy, while she can feel love (or something, their relationship didn’t turn out to be very healthy) towards Spike.
And speaking of Joss Whedon musicals (how many of those does he have now, like two?), there is Doctor Horrible’s Sing Along Blog. There’s not a sung reprise in this one that I can recall, but again with the character lietmotifs, in this case of Dr. Horrible and Penny. Aside from being the themesong of the show, Dr Horrible’s tune plays in the background from time to time when he’s scheming on something (actually, I think it only shows up outside of the theme song when he is stealing the Wonderflonium).
After seeing Dr. Horrible basically be the helpless nerd that Captain Hammer beats on, when one of his plans looks to actually work, we are treated to him singing his theme song, with the lyrics being about how he intends to cause massive anarchy, take over the world, and murder Captain Hammer (all three things which Penny, the girl he is trying to impress, would presumably not approve of). After the end of the show, the credits come on with a piano reprise of Penny’s Song/Caring Hands, only for the song to suddenly get trampled over with Dr. Horrible’s Theme again, reflecting how he lost the one he love (or, well, the one he was infatuated with, anyways) in the course of gaining membership to the Evil League of Evil (he should have seen it coming, it being a Joss Whedon production)
In Hair, “Manchester England” comes back for a verse near the end with a much different tone in “The Flesh Failures (Let the Sunshine In)”
It’s very touching.
Okay, that’s fair. But what you have to keep in mind is that Lloyd Webber has been highly criticized for doing just that. Some (usually the highbrow, Sondheim et al. fans) say that he uses the same melodies in inappropriate places for the sole purpose of grinding it into audience’s ears, so they’ll be humming the tunes as they leave the theatre. And it really is true… I’ve seen dissections of his shows where they’ll illustrate how polar opposite characters (i.e. Judas and Jesus, Phantom and Christine, etc.) will sing the exact same melodies at different points in the show, which really doesn’t make sense in the context of the plot.
“True” musical theatre composers, the kind usually praised by critics but never heard by the masses, don’t do this very often because they understand that the music should be true to the character, and should reflect their state of mind in that very moment. The song I quoted from Gypsy earlier is a good example, because she sings “Small World” with Herbie when they first meet each other. Then in the second act, when her life has gone to hell and Herbie leaves her, she sings a mournful version of it by herself. It works for two reasons: 1) She is one of the characters that sang it in the first place, and 2) That’s what people do when they break up; they think back to how it all began.
Having said all this, I will agree that it is a convention that’s common in musical theatre. It just needs to be done right to be effective, and not used in such a way as to just sell albums after the show.
In The Music Man, the slow and wistful “Goodnight My Someone” is the same tune as the rousing and upbeat “Seventy-Six Trombones.”
And in a brief reprise toward the end Harold and Marian sing both songs, alternating one line from each–and halfway through they start singing each other’s song instead. Pretty cute.
I haven’t seen this show in a long time, but ISTR that “As Long As He Needs Me” from Oliver is about different people from the original singing to the reprise. The song is sung by nancy, and the “he” refers to Sykes; she’s saying that she’ll do whatever he needs her to do with no questions asked, regardless of the consequences. As the play goes on, though, she increasingly sees the immorality of what Sykes is up to and decides she must protect Oliver at all costs–including the cost of her own life. So in the reprise the song’s about how she’ll never betray Oliver’s trust. The words work equally well for both characters.
Now someone will come in and tell me I’m remembering this all wrong–
That’s the one I was going to post. “Don’t let it be forgot…that once…there was a spot. For one brief shining moment. That was known as Camelot.”
The obligatory TV Tropes links, because someone has to go out there and be evil: Dark Reprise and Ironic Echo.
Joss Whedon, of course, does it worst in Doctor Horrible’s Sing-Along Blog. “And I won’t feel…a thing.”
In the musical TITANIC, the opening montage of “In Every Age” and “Godspeed Titanic” is reprised at the very end with the survivors, wrapped in blankets, making their way back to the sides of their now-dead friends, husbands, colleagues, etc.
I think all the examples have a reprise that is more melancholy or downright tragic. Are there any examples where the reprise is more upbeat and optimistic than “prise”?
Is there a term for the first time a melody is played before the reprise?
I asked about the “Honey Bun” reprise in a recent thread, and still don’t get it. Most of these recast reprises make some kind of sense, lyrically. But “Honey Bun”? I got nothin’. The closest the previous thread came to explaining was that it was just a catchy tune the soldiers could march to. Then why was it so downbeat? It just seems like another song would have worked much better - either a completely new song, or a reprise of “Cockeyed Optimist”, which could at least have been given a “Whistle A Happy Tune” function as they marched off to war. (Yes, yes - I know the soldiers hadn’t heard Nellie singing that song the first time around, but still.) Any other ideas?
One of the most famous recast reprises is also from Gypsy: “Let Me Entertain You”! From a cute kid’s vaudeville song to a sexy striptease number with (IIRC) no lyrical changes - quite a feat. Plus, one of the exceptions to the rule that most of these reprises are happy songs turned melancholy.
Lloyd Webber is a “true” musical theater composer, and quite a good one at that. While he does sometimes drive the same melody home a few times too often, in principle there’s nothing whatsoever wrong with having different - and even polar opposite - characters sing variations on the same song.
Anyways, I rather like the reprise of “There’s No Business Like Show Business” from Annie Gets Your Gun (e.g.). It’s not so totally different from the original, but it’s interesting how it’s used to reflect on how far the character has come in a short time.
All in one exquisitely calibrated, beautifully langorous crane shot. Wonderful. 
There’s no way I’m going to derail this thread by getting into a big Andrew Lloyd Webber debate, but this–especially my bolded part–is categorically, unequivocally false.
Look, I’m a fan of the guy. Superstar is what introduced me to musical theatre in the first place, and I also love *Evita *and Sunset Boulevard. But there’s a difference between using reprises of melodies to further enhance the story, and being lazy. Giving polar opposite characters the same melody is just that; lazy. The music should establish a character’s entire personality… his or her goals, moods, desires, everything. And you can’t do that effectively if you just recycle the same songs. I won’t even go into how he uses the same songs in different shows.
My example is from The Sound of Music as well, but the song I thought of was “Maria”. The nuns sing it early on to introduce us to the character and to sort of run down the problems she’s having as a nun - she runs, she sings, she wears curlers. “How do you solve a problem like Maria?” they ask. Well, that’s answered toward the end, when the song is used as the bridal march during her wedding. Evidently, the solution was to marry her off - she was never any good as a nun anyway.
“Music of the Night”, ditto. Goes from “help me make the music of the night” to “it’s over now, the music of the night.”
Except when it’s true. There’s no musical “truth” that is wholly universal, with no exceptions whatsoever. Because we will find you an exception. 
And here’s where I’m gonna show you the exception (and answer your OP too!). Mary and Judas in Jesus Christ Superstar both sing “I Don’t Know How to Love Him.”
Mary’s a dewy-eyed whore who sings IDKHtLH out of romantic/spiritual love with Jesus, emotions that confuse her because she’s only used to dealing with men in a sexual way. Her version of the song is filled with longing, awe, and acceptance of this new feeling Jesus inspires in her.
Judas is a pragmatist who’s just betrayed his best friend in order to save his people (so he thinks). He sings IDKHtLH in bleak acknowledgment of the magnitude of his crime and is desperate to express that he still loved Jesus, even as he betrayed him. He fears he’ll be haunted by Jesus until Jesus dies … or until, he comes to realize, he himself dies. The song represents his realization that he can’t deal with both loving Jesus and having killed Jesus, and leads to his suicide.
If you have a good lyricist, using the same music for diametrically opposed characters can indeed have a purpose. ALW’s problems (which, let’s face it, he’s taken all the way to the bank!) arose when he partnered with a dud lyricist rather than the incisive Tim Rice.
Moving on…
I’ll go with “Tonight” from West Side Story. First time it’s a hopeful, soaring declaration of new love. Second time Maria and Tony’s duet becomes a Quintet, their love song competing against the backdrop of the approaching rumble between the Jets and Sharks, and also the lusty fantasies of Anita, who’s looking forward to sexytimes with Bernardo.
Sondheim performed a similar transformation (one that was quite possibly influenced by his work on WSS) in Sweeney Todd with “Johanna,” which is first a solo by Anthony sung in besotted, heroic tones after seeing Johanna for the first time and discovering she’s a ward of a creepy judge who doesn’t let her out of his sight. In the second act, Johanna has a different sort of ‘cage’, and has gone missing entirely. Anthony sings “I feel you, Johanna” in hopes that he’s getting closer to finding her. Meanwhile, his yearning is played against an entirely different song (also called “Johanna”) sung by Sweeney Todd, who’s missing his daughter ‘less and less’ while continuing his murderous activities.