No need to rehash the virtually unanimous praise of the movie in this thread, but I will anyway: It was one of the best film experiences I've ever had the pleasure to indulge in.
What I, as a musician, found kinda interesting about the ending... I'm talking about the
very last scene and last pieces of the score being played... is that the final chord played on the strings employs a Picardy Third. This is a technique in which a piece of music resolves its last chord to the parallel major tonic in a minor key. In layman's terms, a somber, sad, or melancholy feel that the music evokes is abruptly turned on its head
only on the final chord into a bright, happy sounding resolution. Normally, music can and does transition from a minor to a major key often, but it's almost always done in an organic, flowing way through gradual modulation of shared tones, chords or melodic "hooks" over time,
not instantaneously at the final tonic resolution. It sounds forced, hollow, disingenuous and "fake", and Picardy Thirds are rarely employed in modern music in this particular way... it's primarily a Baroque technique iirc. To quote the wiki entry:
"According to James Bennighof: "Replacing an expected final minor chord with a major chord in this way is a centuries-old technique—the raised third of the chord, in this case G♯ rather than G natural, was first dubbed a 'Picardy third' ("tierce de Picarde") in print by Jean-Jacques Rousseau in 1797 ... to express [the idea that] hopefulness might seem unremarkable, or even clichéd "
I realize this is a very pedantic analysis of such a cool moment, but I feel the chances of the composer employing this technique as mere whimsy or a happy accident instead of deliberately is quite slim. It gives a somewhat jarring, unexpected, and (possibly) uneasy resolution to the musical, and indeed emotional, landscape of what just happened in the movie. Its happy tone is an illusion of sorts, as the resolution is not given enough preparation (musically) to feel convincing.
Perhaps it's a musical reinforcement of the WTF that just played out before us... perhaps it's a final, sarcastic depiction of Thanos's emotions: brooding sadness through his ponderance of what he accomplished (what did it cost you... everything) yet a brief sense of shallow pride, victory and happiness, as indicated by his smirk... or perhaps it's just a simultaneously brilliant yet whimsical compositional gesture by the composer of the film without a deeper relevance at all.
Either way... just thought I'd share a unique perspective on this moment