There is a particular danger in making music about the stuff beneath things. Eventually one starts talking about substance, immanence, matter, becoming, hidden layers and other words that seem to have been invented specifically to frighten people away from the listening chair. François J. Bonnet, fortunately, knows the difference between an idea and an explanation. Under his Kassel Jaeger alias, "Sub Re" approaches sound at its most physical while refusing to pin it down, producing a forty-two-minute work in which material is constantly appearing, receding and changing its apparent identity. The title, derived from the Latin expression for what lies beneath the thing or beneath matter, is therefore less a philosophical label than a listening instruction. Do not stop at the surface.

Bonnet is particularly well placed to investigate such territory. The Franco-Swiss composer, writer and theorist has directed INA GRM since 2018, inheriting responsibility for one of the crucial institutional histories of musique concrète and electroacoustic research, while maintaining a substantial practice of his own as Kassel Jaeger. His work has long occupied the uneasy territory between concrète experimentation, ambient noise and electroacoustic improvisation, and his collaborations with artists as different as Éliane Radigue, Oren Ambarchi, Jim O’Rourke, Stephan Mathieu and Akira Rabelais suggest an appetite for sound that refuses to behave according to genre etiquette. "Sub Re" feels like a particularly concentrated expression of that attitude: rigorous in construction, but much less interested in demonstrating its credentials than in making the listener uncertain about what is actually being heard.

The opening of “Sub Re (Part I)” is almost aggressively material. A thick, abrasive mass arrives before anything resembling conventional musical orientation has been established. There are hints of amplified strings, feedback, low-frequency pressure and electronic resonance, but identifying each component would rather miss the point. Bonnet does not present sounds as objects on a table. He allows them to contaminate one another until texture becomes event. A harsh surface can suddenly acquire depth; something that initially seems electronic begins to suggest an acoustic vibration; density collapses and leaves behind a much thinner trace. The ear is repeatedly forced to revise its assumptions, which is considerably more interesting than simply being told that a sound has been “processed”.

Then come the bells, or something sufficiently bell-like to make the distinction increasingly irrelevant. Their metallic presence introduces a different kind of temporality. Instead of the blunt pressure of the opening, we get intervals, resonance and decay, with individual strikes leaving enough space for their surroundings to become audible. The effect is surprisingly physical. These sounds do not decorate the composition; they establish distances within it. Their reverberations seem to measure the space in which the rest of the music is occurring, while the surrounding electronic layers keep altering the apparent dimensions of that space.

This is one of Bonnet's great strengths throughout the album: he understands that the identity of a sound is partly determined by what happens around it. A tone can be comforting or threatening depending on the pressure beneath it. A field recording can suggest an actual landscape until a synthetic layer quietly changes its meaning. A sustained frequency can resemble an organ, an electrical fault, wind, or simply the acoustic equivalent of having forgotten why you entered a room. "Sub Re" repeatedly exploits these shifts without turning them into cheap surprises.

The album's use of source material is particularly effective because Bonnet's concrete approach does not result in the usual parade of recognisable found sounds. Some elements originated in earlier works and performances, including material connected with projects presented in Venice and Sion, but once detached from their original circumstances they are no longer treated as archival evidence. They become available for recombination. This is crucial. "Sub Re" is not an anthology of sounds Bonnet has encountered; it is an argument for what happens when sounds lose their biographies and acquire new relationships.

The second half deepens that process rather than simply providing a calmer counterpart. A heavier, more organ-like presence gradually gives way to tones that seem almost illuminated from within, followed by environmental details that open the composition outward. At points, the music feels unexpectedly close to a landscape recording, but the impression never settles comfortably. The natural world arrives already filtered through technological perception, while the electronic material starts behaving with an almost organic patience. This ambiguity gives the album its peculiar emotional temperature. It can sound expansive without becoming picturesque, beautiful without becoming decorative.

That distinction matters because "Sub Re" is much less interested in atmosphere than many records that might be filed under ambient music. Atmosphere here is unstable. It is something produced by the interaction of materials rather than a permanent mood supplied in advance. One passage may feel submerged and claustrophobic; another suddenly seems to expose a huge horizon; then the horizon disappears and the listener is left with a residue of vibration. The transitions are not merely connective tissue. They are where the music actually thinks.

Several outside listeners have responded to precisely this quality, noting the record's unusual narrative continuity despite its abrupt changes of texture and register. One review describes it as difficult to remember in purely verbal terms, yet repeatedly rewarding on return, while another hears the two long pieces as a sequence of shifting environments rather than conventional compositions. Those observations get close to the album's real achievement: "Sub Re" is highly composed without constantly advertising the fact that it has been composed.

There is also a certain slyness in Bonnet's handling of grandeur. The album can become enormous, but it rarely settles into the grandiose. A swelling passage might suggest some monumental revelation, only for the composition to withdraw and leave a much smaller sound behind. This prevents the music from confusing scale with significance. Plenty of experimental electronics have mistaken loudness, duration or density for profundity. Human beings do enjoy putting three large words next to a thirty-minute drone and declaring the universe solved. Bonnet is more disciplined than that.

The Victor Hugo connection gives the title another dimension. "Sub Re" alludes to a section of "The Toilers of the Sea" in which a man confronts an apparently impossible task beneath the surface of a wreck, surrounded by water, currents and the forces of the sea. Bonnet's music does not illustrate this literary scene, and thankfully there are no shipwreck sound effects waiting around the corner. Instead, the association offers a useful metaphor for the album's compositional method: action happens below the visible surface, where perception becomes less certain and intuition has to replace stable landmarks.

That makes the record's silences and withdrawals as important as its more spectacular eruptions. Bonnet is not simply piling material on top of material. He is continually adjusting the pressure between presence and absence. When a dense passage disappears, what remains is not emptiness but a newly exposed sensitivity to smaller details. When a sparse passage thickens again, its weight is felt precisely because the ear has been recalibrated. The music breathes in terms of concentration rather than rhythm.

The two-part structure is consequently more convincing than a collection of shorter tracks might have been. Each side has enough time to establish a situation, undermine it and find another one without rushing towards a recognisable conclusion. The result is less like a suite in the traditional sense than a continuous negotiation between incompatible states. There are traces of noise, drone, musique concrète, environmental recording, electronic abstraction and something surprisingly close to instrumental music, yet none of these identities gets to take possession of the album.

Bonnet's own theoretical writing is often concerned with what sound can become before it is reduced to a fixed meaning, and "Sub Re" gives that question a remarkably tactile form. The record does not ask us to identify the raw material. It asks what the material can do once its original identity has become unstable. A bell can cease to be a bell. A field recording can stop being a document of place. Feedback can become a horizon. A drone can acquire the nervousness of weather. Nothing has to remain itself in order to remain recognisable.

The artwork by Ron Jude and the physical presentation reinforce this sense of unstable perception, while Giuseppe Ielasi's mastering is an especially appropriate choice for a work so dependent on fine distinctions between pressure, resonance and disappearance. Yet the album ultimately stands or falls by its refusal to make those distinctions too obvious. "Sub Re" is not a lesson in electroacoustic technique disguised as an LP. It is a record about listening as a process of continual correction.

And perhaps that is what lies beneath the thing here. Not some secret sonic essence waiting to be excavated, but the uncomfortable fact that sound never stays where we put it. We hear an object, then a texture, then a place, then a memory, then something that has no convenient name. Bonnet simply keeps the process going long enough for the listener to notice. The result is demanding without being forbidding, abstract without being bloodless, and occasionally beautiful in the slightly alarming way that beauty becomes more convincing when it refuses to explain itself.

"Sub Re" does not really take us somewhere else. It makes the familiar act of hearing feel less reliable, which is arguably a much stranger destination. And beneath all that matter, pressure, resonance and philosophical vocabulary, there is a rather simple proposition: listen again. The sound has changed.