At this late date, it's surprising how relatively little-known The Dream of Gerontius remains among American audiences. Edward Elgar's masterpiece – even if not the composer's own favourite among his great oratorio trilogy – contains all the goods to move a concert audience to its core. Granted, the devout Catholic theology of redemption expressed by the text Elgar chose to set might initially seem abstruse or intimidating. Yet the source poem by Cardinal Newman, with its depiction of the soul's journey immediately after death and the passage through Purgatory, should, ultimately, be no more inaccessible to non-believers than the vision of John Milton or the rituals associated with the Descent to the Underworld as described by Homer and Virgil in their respective epics.

Moreover, Elgar renders Newman's redemptive journey in psychologically resonant musical terms that are bound to appeal to audiences at home in the late Romantic repertoire. Gerontius inevitably brings thoughts of Parsifal to mind and yet avoids the feeling of being derivative that mars so many other compositions of the "decadent" fin de siècle.

Edward Gardner reaffirmed the uniqueness of Elgar's genius and the immediate impact of his imagination in a performance on Saturday, happily ending a quarter-century Gerontius drought in Seattle. The conductor clearly lives and breathes this music, and Gardner inspired the SSO to give a riveting and moving performance, together with the Seattle Symphony Chorale magnificently prepared by Joseph Crnko and an animated trio of solo singers.

It was a wise decision not to let an interval disrupt the intense focus so masterfully built up during Part I. During the lengthy orchestral prelude, Gardner laid out the framework of the narrative to come, underscoring the tone of anxiety and uncertainty that gives Gerontius its edge. The title character – literally an Old Man, an archetypal Everyman facing the ultimate – is shown to undergo existential terror, no matter how firm the bedrock of his faith. Overall, it's like a psychological allegorization of the darkness-to-light trajectory of the 19th-century symphony.

Gardner tended to favour flowing tempi but showed a sensitive ear for the entrancing blend of colours and polyphonic detail of Elgar's score, its richness all the more extraordinary when one recalls that the composer was essentially self-taught. This translucent approach applied to the admirable balance of choral and orchestral forces Gardner maintained. Despite Elgar's scoring for massive forces, a chamber music-like intimacy frequently emerged, in the sense of the close listening to one another so apparent among the instrumentalists and singers. This yielded ideal results in such pivotal moments as the Proficiscere ending Part I.

Only occasionally I wanted a bit more lingering on local detail, or on the subtle transitions that bind together Elgar's immensely varied soundscape. In a discussion afterward, Gardner pointed to that very variety – or rather, the challenge of making it cohere – as the real heart of Elgar's virtuosity. Gardner paid heed to the composer's rhythmic cues and their larger implications as well: the heavy tread of the bass-line as Gerontius lies on his deathbed, facing the final moments of life ticking away, became a highly effective counterpart to the illusion of pulselessness and the untrammeled horizon of eternity in the opening of Part II. 

The three soloists created powerfully distinctive personalities that enhanced Elgar's dramatic intensity. As Gerontius, Robert Murray made persuasive his transformation from an old man passing away to the Soul of Gerontius facing a new unknown in the afterlife. Murray brought out the various facets of the role in each of these phases: for example, the shift from consoling faith back to doubt and dismay as he repeatedly intones the formula Sanctus fortis, Sanctus Deus on his deathbed. In the afterlife, his phrasing evoked a tender awe.

David Soar used his thunderous bass to commanding effect as the Priest and the Angel of Agony, etching out a vivid sense of character. Completing the trio was Sasha Cooke as the Angel in Part II. Cooke's first-rate performance was one that will long live in the memory. Utterly reliable across her register, she elicited an angelic figure that had nothing to do with saccharine cliche: otherworldly yet deeply consoling, somehow innocent and yet knowing, at moments even anticipating the impact of Messiaen's Saint François

As The Dream of Gerontius reached its culmination, so wonderfully shaped, Gardner conducted with gracefully winglike gestures, guiding the audience through Elgar's musical cosmography with passion. To paraphrase WH Auden, Gerontius strikes the Parsifalian note both as to its pain and its bliss, yet at the end, as the Soul of Gerontius is left awaiting his passage through Purgatory, a hint of Bach emerges – the Bach of the Passions, and specifically the moment of not-quite-resolved suspense as the drama reaches its end, with the Resurrection still lying beyond the horizon.