According to this reviewer's impressions, Modney's album Ascending Primes strives to emulate the prime numbers in their manner of operation: specifically, in their irreducibility, their unpredictability and their inevitability. So what is a reviewer to do, given that the two-disc album succeeds so brilliantly in embodying these attributes? Reduce it anyway? Say something predictable? Evade it by talking nonsense? I am sure I will do all of these things. You were warned, but I do urge you to read on. If I can convince even a half-dozen readers to acquire this album, it will be one of the most useful things I've done with my power as a reviewer. Ascending Primes deserves to be heard and re-heard by as many enthusiasts and sceptics as possible.

Like so much music that I admire, Modney's album juxtaposes complex and simple sound-bits in a way that makes the former seem simple and the latter complex. It's almost a cliché to say so by now. What impresses me most, however, is that these sound-bits are used in an almost traditional manner, like recurring characters in a drama, a classical musical form. Each time an idea returns, it is treated in a new way or re-introduced in light of other recurring sound-bits. We observe these characters either introducing themselves fully formed or inventing themselves before our ears; groping around in the dark and in the light; projecting confidence or diffidence; reacting to the presence of other characters with antipathy, sympathy or equanimity. It's particularly magical when a sound-bit seeks to expand but cannot do so until it's in the presence of another sound-bit, or seeks to contract but loses that desire when other sound-bits are added. When the bits converge, Modney's multifaceted ensemble devises exquisite moments of, simultaneously, transcendence and grounding.

Ascending Primes is in five sections, the last two of which are broken up into four and three numbered and subtitled movements respectively. Each successive section is inspired by an interval, ever higher in the overtone spectrum: unison (fundamental), octave (2:1), fifth (3:1), major third (5:1), harmonic minor seventh (7:1) and augmented fourth (11:1). Their numeric value (and their primality) directly corresponds to the sizes of the ensembles (solo, duo, trio, up to undectet) but is otherwise less important here than the moods, the metaphorical characters that they suggest to the composer. The fifth, for example, suggests ‘honesty and focus’; the third is poignant; the eleventh is ‘a serrated scream’. But this tour of the intervals is not for sightseers. There is a continuous unfolding of successively broader and deeper insights.

The opening movement, ‘Ascender’, features Modney on solo violin, as he presents (aptly) ascending figures with exquisitely tuned double-stops. Dyads are presented here not as harmony but as pairs of tones that provide context for one another. I guess that is harmony, isn't it? But that modality of ‘mutual context-providing’ becomes particularly important in light of the composer's preoccupation with two realms of thought: just intonation and electronic sound.

Just intonation is a sonic world which Modney has clearly thought about and experienced for a long time, viscerally, with a buzzing wooden box jammed against his neck. When two tones form a ‘pure’ interval, they instantly imply a wide spectrum of related tones, unambiguously. Modney hears this spectrum more deeply than we do and demonstrates that tiny changes in one or the other tone just as instantly alter the whole implicit spectrum. The electronic component in turn accentuates the fragility of this purportedly unambiguous soundworld. Throughout Ascending Primes, the electronics are used to make explicit and amplify these spectra, and they intentionally demonstrate that a pair of sustained tones is in no way stable. Difference tones are both indelibly attached to the dyads and imbue them with fluctuations that no notion of stability could possibly countenance.

‘Everything Around It Moves’ forms the centrepiece of the album (being preceded by two shorter and followed by two much longer movements or sections) and is most clearly expository in nature. It begins by presenting snapshots of contrasting sounds, successively cutting from one to the next like an old-fashioned mechanical slide-projector carousel. Even the sound of the projector is composed, in that it is a sound-bit in its own right: snapping with a hard edge, always providing unmistakeable demarcations but sometimes advancing prematurely, impulsively, motivated by its own humours, to the next slide, but also often threatening to jam and thereby bring the slide show to a halt. Children of the 1980s will know the drama that comes with slide projectors constantly threatening to overheat or to betray their purpose and become e-jectors. This in itself is compelling enough, but a disappointed listener who wanted more of it (spoiler: it will return in due course, with even harder edges) is instead treated to the appearance of a much more urgent theme: first the violin and then the piano invent, piece by piece, harmonic progressions, as if such a concept never existed. After what has come before, one could believe that the concept does indeed need to be re-invented every time. Take the familiar and make it unfamiliar. Then make it even more unfamiliar by repetition.

Due to the realities of media, the double-CD version of this album breaks in the middle of ‘Fragmentation and the Single Form’, which is both a practical necessity and a shame. It's a four-track section of the work that really needs to be heard continuously, as indeed the title implies. Those who enjoy collecting physical artefacts are strongly urged to simulate this continuity as best they can. Think of it as a development section in the form: despite its division into movements, Modney and his conspirators are spinning a very thin and vital thread here, and you're likely to miss it if you blink or have to open and close a CD carriage. In the interest of brevity I'll highlight just one aspect of the argument: it seems as though the second half of ‘Fragmentation and the Single Form II: Vox’ invents the notion of groove in the same way that harmonic progression was invented earlier – that is, by interrogating all of its prerequisites and inviting the listener to do the same.

‘Fragmentation and the Single Form III: Song’ is a self-consciously naïve songcrafting exercise featuring the cornet. After all that has come before, this melody formation process is deeply touching and satisfying. Given that we've just learned that nothing a priori exists, Modney composes. He builds up phrases, creates shapes, constructs a harmonic logic as if it could be no other way. All the lessons taught by preceding materials imbue our experience of this song with a sense of deeply personal investment.

I have glossed over so many key moments in this album, and maybe I should actually say nothing about the exquisite final section, ‘Event Horizon’, as I can hardly do it justice and you should be left wanting more. But I cannot close this review without mentioning my immense admiration for Modney's collaborators. It's a nice touch that the very last movement of ‘Event Horizon’ is called ‘Ascenders’, hearkening back to the singular form of this word in the first section's title. Though Modney's name is on the cover, the album feels like it was composed by the whole group. The performers have clearly understood Modney's highly focused vision but have also provided their own perspectives to help enrich it. There is a constant sense that the music breathes – that is, absorbs oxygen into its bloodstream. It yearns for greater harmony, celebrates sound as an indefatigable source of the new. In short, it might make you want to compose too.