In the summer between fourth and fifth grades, Philip Carlsen learned to appreciate the cacophony of sounds that he came to associate with music practice. A 9-year-old cellist at the time, when he showed up for practice each week, the first thing he heard was all kinds of music coming through the open windows of the music school. “I realized afterward or gradually that it was the sound of everyone practicing at the same time, and that made a real impression on me,” Carlsen said.

Those impressions proved lasting, as Carlsen drew on that specific memory when he organized the Elliott Schwartz Memorial Practice Rooms Project, set for 7 p.m. Saturday at the Portland Conservatory of Music at Woodfords Congregational Church in Portland.

It promises to be an unusual concert. Nine composers have written new pieces for multiple pianos, to be performed in eight practice rooms and teaching studios on the third floor of the conservatory. The doors to the practice rooms will be open and the audience will sit in the hallway, “their ears bathing in waves of sound coming at them from many different directions,” said Carlsen, who organized the festival and composed one of the pieces. The compositions last about five minutes each, and each uses all or most of the pianos. The pianists will play together from different rooms, without the benefit of a conductor or the ability to communicate through any means other than the piano.

“There will be chairs in the hallway, and the audience will sit in the hallway,” Carlsen said. “The pianists will be in the practice rooms, so for the most part, the audience won’t be able to see them. The doors will be open, and the sound will come into the hallway.”

The concert is named in honor of Schwartz, one of Maine’s most influential composers, who taught at Bowdoin College and helped establish the Back Cove Contemporary Music Festival. Proceeds from Saturday’s concert will benefit the next Back Cove festival, scheduled to return to Portland in August after a one-year hiatus.

Schwartz, who died in 2016, would have celebrated his 84th birthday this Sunday.

Very likely, he would have embraced this concert. He was an adventurous composer, often turning to uncommon methods and theatrical elements to enliven his music. He composed one piece based on Facebook posts, and another piece included TVs and radios on stage with the performers. A 1966 piece, “Elevator Music,” was performed by 12 small groups on various floors of a building, while the audience rode an elevator and heard parts of the piece on each floor.

Many of the composers who have written music for Saturday’s concert have been involved with the Back Cove festival over the years. From Maine, they include Joshua DeScherer, Nancy Gunn, Bill Matthews, Harold Stover and Carlsen. Francis Kayali from New Hampshire, Josh Jandreau from Massachusetts and Michael Schelle and Miho Sasaki from Indiana are the others. The pianists are some of Maine’s finest players: Bridget Convey, Jesse Feinberg, George Lopez, Gulimina Mahamuti, Chinaru Naruse, Steven Pane and James Parakilas. Carlsen’s son, Melsen Carlsburg from the Boston area, also will join them. All are donating their services.

While the idea for a concert like this has percolated throughout Carlsen’s life, the specific impetus for Saturday’s concert came after the Portland Conservatory began a partnership with Steinway pianos that resulted in several new pianos at the conservatory for students and teachers. “As someone who gets excited about spaces and what you can do with music coming from many different directions, I thought of the idea of putting on a concert where we would write music for each of the pianos up on the third floor. It was kind of a pipe dream,” Carlsen said.

Each composer wrote a unique piece of music with the same challenge of writing piano parts for multiple pianists who would perform simultaneously without being able to communicate verbally or visually, or with anything other than music. Some solve that problem by instructing pianists to start together in the hallway to sync their timepieces and base their playing on timed cues. Another composer wrote his piece based on his vision of the pianos as boats on the harbor, each setting out from a common port on a different journey.

Another won’t share the music with the performers until they sit down at the piano, so each will perform the piece while seeing it for the first time. DeScherer, who previously taught at the conservatory, has written a piece for four pianos and four page-turners. In this instance, the function of the page-turner will be not to turn each page of music but to transport the pages from one piano to the other, room to room – while singing.

Carlsen makes no promises about the outcome of the concert, other than it will be an adventure, and it will be fun. “I feel like it’s really an experiment until we get into the space on the day of the concert,” he said.