The music spiraled off so far from typical melody and harmony, and so deep into the realm of abstract sculpted sound, you had to ask during the Crossing's latest Month of Moderns concert  on Saturday, "What planet might we be on? This time?"

Whistling and Mongolian throat singing merged like long-lost friends. Tone clusters arrived like a mass of computer-generated sound. And embedded in the middle of the piece, by Greek-born composer Efstratios Minakakis, were aggressive vocal trills, something like a futuristic duck call.

Obviously, Mozart isn't in the cards for this Philadelphia chamber choir and certainly won't be in the festival's final concert this Saturday, the world premiere of the nine-movement, hour-long work Anonymous Man by downtown Manhattan composer Michael Gordon.

One of the most forward-looking fine arts organizations in town, the Crossing has made the unassuming Presbyterian Church of Chestnut Hill a cutting-edge choral venue that most major cities simply don't have. And the group has been hitting its highest gear ever during this Month of Moderns festival, bringing in a cross-section of current composers, both from far away and local, in recently written pieces that fall under the heading of Diaspora — as in people displaced from their homelands.

It's safe to assume that Crossing founder/director Donald Nally has Syrian refugees in mind, but he's hardly limiting that idea to current headlines: Minakakis' piece Crossings/Crossings' Epigrams was based on Greek-language quotations from The Trojan Women and Oedipus at Colonus. It dealt with fallen Greek heroes and the wrenching, primordial grief in what the composer calls "en elegy on things irretrievably lost."

Saturday's Anonymous Man promises to be a world away: The title partly refers to homeless people who have lived on Gordon's street. In his libretto, they have personalities, especially when one of them chides Gordon for not reading Aristophanes. And yet they remain somewhat anonymous.

"It's very difficult to get personal information out of someone who is living on the street … it's painful for them," Gordon said the other day. "My feeling is that the best thing I can do is … talk to them. That's a human exchange." His piece also has fallen heroes, including Abraham Lincoln, whose funeral train passed where Gordon now lives.

How this translates into music is — as yet — a mystery. At 61, Gordon has a track record of 70-plus works and is a core presence in Bang on a Can, the collective of New York post-minimalist composers who have dramatically changed the way words can be sung.

He once built a choral work around the names of subway stations. His wife, Julia Wolfe, filled a movement of her Pulitzer-winning Anthracite Fields with names of coal-mining casualties.

For Anonymous Man, Gordon talks about having 24 different vocal lines going at the same time. Before  this week's rehearsals, Nally described the music as highly canonic — looking back to composition techniques from the time of J.S. Bach.

If Bang on a Can composers have a stealth weapon, it's drawing musical energy from the past. "We can't live without the past," said Gordon. "Doctors don't think of how people's legs were sawed off in the 17th century, but we're still interested in Bach. We still have a dialogue with that today."

Not every Crossing endeavor works out. When a choir can do anything — and I sometimes joke that the Crossing could sight-read a blueprint for a hydrogen bomb — the possibilities can be almost too wide open.  Strong overall concepts such as Diaspora can render a piece that's more interesting to talk about than to hear.  Saturday's premiere of un/bodying/s by composer Gregory W. Brown and poet Todd Hearon, for example, which was on the program with the Minakakis work.

The displaced population in this case was from small Massachusetts towns that were submerged with the construction of the Quabbin Reservoir in the late 1930s — with allusions to the supposedly-sunken Atlantis of ancient times. The small-town population said goodbye and went elsewhere. And the tragedy is? For all of poet Hearon's wide-ranging imagery, the worst you could say is that the city of Boston is thirsty.

The music was so dedicated to the fluidity of the verse that whenever you stumbled onto an arresting idea — a quoted church hymn or some madrigal-like counterpoint in the Atlantis section — it dissolved all too soon. And when the music imitates non-oceanic water, expressive intent becomes vague, and a kind of sameness sets in because water — whether hot, cold, clean, or dirty – is pretty much the same.

Well, you never know what a piece has to offer until shortly before the premiere, and maybe not even then. The Greek piece might've been greeted by listeners with bafflement. Instead, the response was more like rapture.

So this Saturday's Month of Moderns finale might be seen as taking a huge chance by devoting the entire concert to the single, entirely new piece by Gordon. But prospective concertgoers can be heartened by the fact that the composer thoroughly welcomes that situation.

"That means I'm setting the expectations. I'm controlling the experience," said Gordon. "It sinks or swims because of my composition. I like that."

The Crossing's Month of Moderns festival concludes at 8 p.m. Saturday at Presbyterian Church of Chestnut Hill, 8855 Germantown Ave. Tickets: $20-$35. Information: