As so often, here is some Saturday morning music; the Letter Duet from Act II of Mozart's The Marriage of Figaro:
I think it is may impossible for me to listen to this piece without tears streaming down my face; although I suppose I could distract and harden myself against its effects if, for example, I was driving a car at the time...
I picked this performance from the many on the many on YouTube by superb performers, because - even though this is roughly recorded and imperfectly balanced due to the live performance; conductor James Levine seems to catch the ideal tempo and instrumental effects - yielding the biggest emotional punch.
Aside from the always delicious combination of soprano and mezzo, what really gets me about this duet is the (mostly) woodwind accompaniment; which is something that is utterly characteristic of Mozart; and so often leads to his very greatest effects and moments.
So, even if you know this already, then perhaps this time you might focus on the orchestra; and regard the voices as instruments.
There is a very simple, rhythmic, arpeggiated accompaniment throughout; upon-which Mozart 'paints' his woodwind effects, and-against which the voices syncopate and overlap teasingly, before joining together in close harmony. The "half-way" moment at 1:27 when everything drops-out for for a moment except the oboe, which plays a descending five-note phrase, is so simple and wonderful that it defies analysis.
Concerning the singing; the melody is occasionally 'decorated' by ascending "grace notes"; when the singer initially hits and accentuates a note below the 'target', before rising to the expected note. This is almost a trope for Mozart - in his instrumental music as well as vocal; he seems to have loved the effect of poignant yearning.
As so often with Mozart's peak experiences (and perhaps especially in this opera); his 'raw material', the action and words in context of the plot; seem everyday, light, trivial... Indeed, in this case the letter is part of a rather sordid plot between the Countess (soprano) and her maid (mezzo) to entrap the Count in a fake adulterous intrigue.
Yet, somehow, Mozart brings a quality extraordinarily subtle and delicate to the piece. And we are raised far above the mundane.