Hey, One of my favorite soundtracks is Z・E・R・O. https://www.youtube.com/watch?v=OncQlCnuv8o
The song reminds me some feelings from the ending of Tsumihoroboshi, It represents perfectly the hope and the impact of this moment.
But there is so much amazing music like “Night When the Invisible Scares You” ( https://www.youtube.com/watch?v=JR0SvgLy_D8 ) , " Wandering Words Lead to Heaven " ( https://www.youtube.com/watch?v=zdEwKBM7jsw )
But I think my favorite music is Birth of the New witch, this song is really perfect it represents ( again…) incredibly well the atmosphere of Umineko. https://www.youtube.com/watch?v=-JBKyLZd6GA Especially the instrumental version. https://www.youtube.com/watch?v=pAkvF7HkFEY
Even if in the end I cannot choose only one, Alive, Life, Engage of marionette, Kina no Kaori, WorldEndDominator, Ridicule, All of this and more, I love them too much.