They sang a capella: one voice began to mount like a skylark and detach itself from the rest, from those mingled voices which together sounded well, but from whose conjunction with this single one soared in an intensity of beauty — a voice so clear and just, yet vibrant with such warm sweetness, I have remembered it always. The fact that this great, this glorious and rare voice was singing behind bars, that the face and identity of this singing nun would forever be unknown to us, shadowed the music. Mainly, we were awed to think this treasure was so hidden.
~from TESSERAE by Denise Levertov