By the end of the 1970s, the “ghosts” in Amacher’s music had become more sophisticated, thanks to a discovery she made while listening to electronic tones for hours at a time. Amacher found that certain combinations of frequencies could, at high volume, cause the ear to produce and amplify tones of its own. Unlike beams of tinnitus, these keening, distortionlike sounds were a sign of healthy ears. (This phenomenon, later called otoacoustic emission, has since been used to test the hearing of infants.)
A filmed 1977 performance of Cunningham’s “Torse” features an Amacher score that reflects this change in her music. The sound mix twirls slow-moving drones and ringing high notes around some of her noisiest, most percussive tones. When played back loudly in an open room, any twist of the listener’s head sets the strange ghostly sounds loose.
In 1980, the conductor Dennis Russell Davies turned over his home in St. Paul to Amacher; she proceeded to transform the space into one of her multiroom sound installations for that year’s New Music America festival. She loaded the house with speakers, hiding them under stairwells, behind walls and in closets. Then, at high volume, Amacher mixed prerecorded tones from her library of tapes with the ambient sounds she had observed in the house.
This was not a style suited to recordings, and Amacher’s psychoacoustic effects can’t be experienced through headphones. The composer and electronic music pioneer Richard Teitelbaum, who played with Amacher in MEV, said in a recent interview that even the best-pressed vinyl couldn’t capture her music. “Anything too soft didn’t come through too well,” he said. “So letting somebody play one of her records in the living room while other people are talking or eating or whatever was quite far from what she envisioned.”
Only a few recorded examples of Amacher’s visceral works are available. A clip of the New Music America installation appears on the compilation “OHM: The Early Gurus of Electronic Music.” She issued two discs’…