Only the Sound Remains consists of two stories of supernatural encounters. A monk, praying for the soul of a deceased general, meets the latter's ghost, attracted by the sounds of the lute used in the monk's ritual. A fisherman finds the feather mantle belonging to a Tennin, an angelic spirit, who pleads with him to return the item, which he only does after she performs a celestial dance; thus, the chorus tells us, ‘was the dance of pleasure, Suruga dancing, brought to the sacred east’. Both encounters are evanescent: the ghost of the general is visited by memories of terrible battles and disappears back into the spirit world; the Tennin's dance is an announcement of spring, as the Tennin herself disperses into the mists that obscure mount Fuji. In both stories, the spiritual is a manifestation of something virtual, relating artistic forms to worlds not of, yet touching on, the everyday. The sounds of the lute, which used to belong to the general, are a conduit to deep memory; the dance taught by the Tennin connects humans to the inhuman workings of nature.

Premiered by the Dutch National Opera in March 2016, Kaija Saariaho's twin opera, after Ezra Pound's translations of two Noh plays, is scored for small forces: apart from bass Davone Tines as priest/fisherman and countertenor Philippe Jaroussky as ghost/Tennin, there is a dancer (Nora Kimball-Mentzos as the dancing body of the Tennin), a four-voice choir and an orchestra consisting of string quartet, flute, percussion and kantele, all supplemented by electronic sounds. Peter Sellars's staging is similarly modest, making effective use of a simple set design by painter Julie Mehretu, whose complex abstract graphics on a large sheet (one design per opera) form a semi-transparent curtain, with the main characters variously positioning themselves in front of it, to the side of it, or (as supernatural beings) behind it. The sheets show themselves in constantly transforming ways as they are lit differently throughout the performance. During the final dance, the sheet is lifted, revealing the depth of the theatre space with a second, identical sheet in the distance, suggesting the vastness of Nature as represented by the Tennin's dancing.

Saariaho's musical idiom is grounded in harmony and texture, and she makes adept use of the limited forces at her disposal to generate a variety of atmospheres. Instrumental writing largely is in the service of texture, and as a result its lines tend towards the ornamental. By contrast, there is at times some very beautiful, relatively uncomplicated writing for the solo voices, especially in the otherworldly countertenor part, wonderfully performed by Jaroussky. The most important element of the musical discourse, however, may well be the use of electronics, a counterpart to the opera's dramatic subject: the encounter with the spiritual or the virtual.

In the first place, electronics help to amplify the modest ensemble so that it can hold its own in spaces devoted to grand, nineteenth-century opera. This makes the chamber group sound bigger than it is (whilst keeping the production costs down) and gives it a kind of hyper-real immediacy as the electronic mediation brings the sound everywhere in the hall, rather than inviting the listeners to incline themselves towards the sound. The ironic result is that it hardly ever achieves the sort of chamber-like intimacy that do, say, Wagner's grand orchestras.

The prime musical effect added by the electronics to the sound is the extension and transformation of reverb, especially strong when applied to the resonances of the plucked strings of the kantele. Such extended reverberation effectively evokes the spiritual realm, but, strangely, also ends up making the virtual quite literal. When the choir connects the evocations of the lute's strings to memories of life – ‘The bass strings are something like rain … the third and the fourth strings are like the crying stork in her cage’ – it is slightly confusing to hear the magic of string resonance being aided, amplified, and brought to you directly through electronic mediation.

This problem is treated very differently in the second opera, about dance. Here, the electronic spirit world appears more strongly contrasted with the instrumental world; manipulation of reverb is more explicitly applied to the Tennin's role only, and during the dance climax, the instrumental ensemble starts sounding more like a chamber group, the individual instrumental idioms becoming more focused and directed. This gives the second opera a clearer, more immediately satisfying dramatic arc. It is as if the fusional nature of the first opera – ghost/memory/music/string resonance – makes its subject matter too delicate for the grand, public treatment required by opera houses. In the second opera, its subject matter – dance/nature – constitutes a clear Other, and maybe that is what makes it more amenable to operatic treatment.