Cutting-edge music in a vast West Philly church, brought to you by Bowerbird (Who else?)

Music at the edge always keeps audiences mentally on the move — but on Friday and Saturday, April 12 and 13, listeners will physically migrate from room to room at the sprawling Holy Apostles and the Mediator church in West Philadelphia to hear the unprecedented sounds and evolving creative stages of one Maryanne Amacher, composer and installation artist.

The three-part program is part of an Amacher mini-festival with the imagination-tickling title Perceptual Geographies. It is being presented by the Philadelphia concert organization Bowerbird, known for previous retrospectives of John Cage, Morton Feldman, and Julius Eastman.

An introductory talk opens the festival Tuesday. There’s a workshop Saturday afternoon.

Amacher (1938-2009) created electronic-music installations, sometimes showing up with a box full of tapes whose contents were known mainly to her, and arranging speakers in the rooms according to her aural theories. Sometimes, speakers were under the floorboards, creating three-dimensional sound shapes that hit listeners in unprecedented ways.

She went into high gear about the time the experimental artists of the 1970s gave up. Whether at the University of Pennsylvania or at her reputedly chaotic headquarters in Kingston, N.Y., she explored sound perception in a way nobody had.

“She represents a lost thread in American music," says Bill Dietz, co-chair of Music/Sound at Bard College, where Amacher taught. "A certain lineage or direction just stops with [avant-gardist] John Cage, almost as if it was this weird thing that just petered out. But for Maryanne, Cage was a starting point and kept going … that was so far out and so much on her own.”

Because many of Amacher’s works weren’t written down, Dietz is resurrecting installations in the festival that follow the spirit rather than the letter of her work. She died falling and hitting her head while teaching a class at Bard – leaving her devoted band of followers guessing how her music can be reassembled.

This isn’t unique to Amacher. “We’re facing a scoring crisis,” said Bowerbird founder Dustin Hurt. “That generation of artists who have died in the past 10 or 15 years often left a huge body of work that’s not in any traditional scoring. A lot is going to be forgotten, or just documented in photos and videos.”

Amacher’s evolution was dramatic, and replicating it can be more or less impossible: One of her last pieces, for example, was an installation that had 40 speakers positioned in various parts of a square in Mexico City.

In the Philadelphia mini-festival, her 1965 Adjacencies for percussion will be in the church auditorium. Petra, for two pianos, one of the last pieces she wrote down, will be in the sanctuary. Sound installations are planned for the basement gym with its colorful murals.

Resembling a professorial, slightly disheveled version of Gloria Steinem, Amacher in later years often approached music as a scientific researcher. In her four-year residency at the Massachusetts Institute of Technology, she had sounds from Boston Harbor piped into her studio in an effort to locate the basic tones that defined that environment.

More important, she explored how the ear augments and changes whatever sound it hears and wrote music that somehow intended to illustrate that. In effect, she looked at music through a microscope — and then wrote pieces that took the listeners inside the microscope.

The pieces could sound like anything from the inside of a giant church bell to a severe weather alert on your smartphone to a UFO parallel parking in front of your home – all embedded with “spirals and purrs and sound in various shapes,” as Amacher described what the ear unconsciously adds.

The idea, said Dietz, is that “we would be listening to ourselves."

Those two interests – environmental tones and how the ear perceives sound – came together in Amacher pieces that have no beginning or end but that are installations that continue over weeks, months, years.

Her inspiration? TV series and comic books. She loved continuous stories and hoped her installations would be enjoyed in a similar spirit. “People hear them, they go away, they tell other people. A real dialogue is set up,” she said in one of her lectures.

It’s no wonder that she never finished a commission to write for the Kronos Quartet, which would’ve brought her name into the classical-music mainstream but would’ve required a beginning and end.

The 13-year-old Bowerbird organization has been known to cast a wide net for appropriate venues. Its headquarters at UniLu (University Lutheran Church) at 3637 Chestnut St. is convenient and has allowed an expansion of its concert season – 20 concerts in the first half of 2019 — but the larger campus of Holy Apostles and the Mediator was needed to encompass a cross-section of Amacher’s work.

Less radical but challenging in its own way is the combination of voices and percussion in Moonlite, a dramatic new work for chorus and percussion by emerging composer Wally Gunn. That one, about the 19th-century Australian outlaw Andrew George Scott — known as “Captain Moonlite” — is on the Bowerbird concert schedule next month, premiering May 16.

Developed over several workshops by the Philadelphia vocal sextet Variant 6 and New York’s Mobius Percussion, Gunn’s 90-minute piece – with its picaresque subject matter and texts taken from Scott’s writings while on death row – required the versatility of the Maas Building on North Randolph Street, whose spaces also host weddings and graduation parties. The audience can be counted on to find it.

“A lot of new-music enthusiasts in Philadelphia trust their brand,” said Steven Bradshaw, a member of the Variant 6, which has collaborated with Bowerbird on previous events. “So when they plug their audience into our sound world, which may be less familiar to them, we benefit greatly.”

For Gunn, the story of Scott (1842-80) — robbing banks and expressing passion for a man he met in prison but later lost in a shoot-out — is a distant refraction of what is now called “queer culture.”

“His writing can be viewed as the height of 19th-century romanticism, or very direct references to homosexual love,” said Gunn, a native Australian. “Queer historians might argue that there was no such a thing as gayness then … but struggling with being an outsider is in the queer experience.”

How can this operatic romanticism be part of the same mission statement that embraces the fearlessly cerebral Amacher? On Bowerbird’s website, the sentence “We specialize in …” keeps being finished with different words: “experimental … unknown … forgotten … rediscovered.”

The Gunn piece itself promises to be a hybrid, not telling the story in a linear way but zeroing in on key plot points and exploring them in a huge variety of vocal and percussive means.

“Men will sing in falsetto. There will be unflattering vowel sounds at times to convey harshness,” said Gunn. “Sometimes it’ll be more like being inside the head of the some of the characters and the many voices we live with inside our heads.”

So Gunn and Amacher both delve into the mechanics inside the human skull. But don’t most artists?

MUSIC MINI-FEST

Maryanne Amacher: Perceptual Geographies

The Amacher mini-festival opens with “Maryanne Amacher: An Introduction,” Tuesday, April 9, at the Kislak Center in the Van Pelt-Dietrich Library, 3420 Walnut St., sixth floor.

“Adjacencies,” “Petra,” and the sound installations are at 7:30 p.m. Friday and Saturday, April 12 and 13, at Holy Apostles and the Mediator, 260 S. 51st St. Tickets: $15-$30.

“Ways of Hearing,” a workshop, will be held at 1 p.m. Saturday, April 13, at Holy Apostles.

“Moonlite” will be premiered May 16 at the Maas Building, 1325 N. Randolph St. Tickets: $20-35.

Information: bowerbird.org.