@AndrewH shared his beautiful Orchestra performance here Lili Boulanger's "D'un soir triste" - a VERY powerful, sad piece!
Lili Boulanger didn't have an easy life, witnessed the time of WWI and died at 24, so she wasn't a stranger to sadness - but how did she achieve all this emotion in "D'un soir triste"?
...I happened upon a 3 Video analysis on YouTube (andyanalysis), The Magic of: "D'un soir triste".
The 1st Video takes a closer look at Lili's Harmony, Rhythm, Melodic development... and more.
This 2nd Video looks at the Jazz elements - ahead of her time?
The 3rd Video looks at the effect of the low notes and the Phrygian mode, then how complex harmony, polyrhythm & dynamics play important roles at the end!
These videos make references to elements discussed in other Music Theory threads!