Biologists discover entire worlds in a drop of water; inventors store them on a microchip. But time and again, composers were heard distilling complete worlds within the confines of 21 voices and 20 minutes at the closing concert of the Month of Moderns festival by the Crossing. And it wasn't always pretty.

Most typically, unaccompanied voices inspire consolidated, contained expression, though not in various works heard Friday at Presbyterian Church of Chestnut Hill by Bo Holten, John McCabe, and in an important world premiere, Philadelphia's Kile Smith.

"How did they write down these fantastical effects" was my ongoing ingenuous question, followed by "How did the singers do that?" Under the Crossing's founder/director, Donald Nally, the chorus sang (to borrow a current film title) like angels and demons as the music requested, every vocal department being, at one time or another, astounding.

McCabe's 1986 Scenes in America Deserta uses words only as a platform to dramatize the natural chaos of the nonhuman world, ending with the rumbling underlying hum of the planet, subtly undulating and constantly evolving. Holten's 1991 masterwork, Rain and Rush and Rosebush, has the Hans Christian Andersen text about the trials of life positioned on canvases of sound, full of contrasting foregrounds and backgrounds with sopranos in rapture and everybody else portraying a larger society with malicious nattering and intractable domination. It felt like a holograph in sound.

Smith's Where Flames a Word took on Paul Celan poems that seem to be about soul recognition through sex - in words too fearlessly personal to be uttered in real life and that can perhaps exist only in a poem. The depth of expression easily surpasses his much-discussed Vespers. Some of the word settings are plainspoken as can be; others sail in through alien key signatures, racing in from some side door. Resolutions got sidetracked by bass notes that rise from under cover. Most of it makes little literal sense but, poetically speaking, feels completely right in spellbinding ways I never imagined.

Where Flames the Word will be reprised at the Crossing's free opening concert of Chorus America's National Conference, 7:30 p.m. Wednesday at St. Peter's Episcopal Church, 313 Pine St.

Other, smaller works felt at home on the program thanks to their meditative nature, such as "Voices of Autumn" by Jackson Hill and Paul Fowler's "Potter's Clay." But what suffered in comparison with the rest was Arvo Pärt's I am the true vine. Though Pärt is one of the mainstream stars in choral repertoire, his music is often a spare reflection of something too profound to be encompassed. But without a strong sense of that something larger, you're left with some fairly wispy music (as was the case here). At least the piece offered breathing room in an admirably dense program.

Contact music critic David Patrick Stearns at 215-854-5598 or dstearns@phillynews.com.