I think I am not alone amongst audiencegoers: I love opera, often enjoy choral singing, and am even occasionally enchanted by Lieder, but purely instrumental music, if it's not actively transporting me from one scene of Wagner to another, really doesn't grab me all that much (though of course I like a soothing piano sonata in the bath as much as the next person). I always thought I was too obsessed by words and narrative, and what composers did with them, to want to also get involved in their more abstract evocation of – what? What does any given quartet or concerto mean? What is it designed to achieve, to provoke, to explore? However, although I had undoubtedly come to Snape that evening solely in order to hear Ian Bostridge sing Britten and Tippett, I left feeling the most astonished, and exhilarated, by Britten's extraordinary String Quartet no. 1, played with blistering skill and forensic intensity by the Arcadia Quartet.

In a change to the published order, Bostridge began proceedings with Tippett's The Heart's Assurance, a chain of five unsettling songs setting tragic poems by Alun Lewis and Sidney Keyes, poets who both died in the Second World War, culminating in the exceptional, insistently humane Remember Your Lovers. Drake's velvet-fingered accompaniment never faltered in its thoughtful, expressive power. Bostridge, animated by dynamic energy which seemed to thrum from the soles of his feet to the crown of his head, often clung to the piano with one hand as he swayed or shifted while singing, regularly favouring one side of his mouth. While the subtlety and diversity of the sounds and textures Bostridge creates is beautiful and impressive, from burnished lows to floating highs, this delivery causes trouble with his clarity of articulation, and I found myself increasingly checking the programme to find out what he was singing. Perhaps aware of this, Bostridge employed some sharply over-emphasised consonants to close and open words, which in turn became distractingly synthetic. While Compassion sounded richly resonant, only Remember Your Lovers came over with the insistent urgency, and sense of emotional command which these troubled and troubling songs need, inspired by Tippett's grief and anger at the war, and at a close friend's suicide.

We moved on to the Sechs Hölderlin-Fragmente cycle by Britten, a cycle of six songs in which Sokrates und Alciabiades shone with its strong overtones of Death in Venice, and Hälfte des Lebens took me straight to the luscious, florid and decaying world of The Turn of the ScrewDie Heimat was almost unbearably beautiful, with a certain pastoral freshness to its lines. Bostridge's delivery remained taut, impassioned, and superbly controlled, but still mannered.

Britten's String Quartet no. 1 had a tremulous, magical opening into which larger notes fell like huge raindrops scattering onto a wind-harried sedge, finding strange synergies between notes, before plunging into a journey in which the violin is the hero. Ideas evolve from a deep and changing harmonic structure, like bubbles floating to the surface of a deep lake. Different movements finish with a sprightly flourish, almost a touch of insouciance. The Arcadia Quartet's superb playing had the audience spellbound, while the whole piece seemed to express a complex and sophisticated joy, one which is not achieved without pain and endeavour along the way.

With Steven Osborne taking his seat at the Steinway after the interval, Tippett's Piano Sonata no. 2 unfolded like a complicated person in a hurry to explain themselves and justify their actions, veering in seconds from delicate passages of filigree softness to chords of almost violent drama. As the different elements cut across and intersected, I began to see that the piece needed both sides of its complex personality; too much sweetness would have been entirely saccharine, and too much aggression beyond listenable, but the interplay and contrast made for a interesting, dynamic whole.

As he returned to the stage for Winter Words, Britten's setting of Hardy's poems, Bostridge's characteristic delivery now seemed so standardised that it risked caricature: his gestures, his manner and approach all still unchanged from the former pieces, the performance overall seemed less than fresh. Articulation was problematic here, not so much of words as of emotions: while he found almost too much righteous anger for The Choirmaster's Burial, the poignant Wagtail and Baby came across with very little emotional definition. The poem is a classic Hardy vision of deception, betrayal and its horrific consequences: an abandoned baby, left by a stretch of water, watches a wagtail (the symbol of its lost mother) survive encounters with other symbolic animals, only to see her finally fall victim to "a perfect gentleman". Bostridge's reading seemed rather longer on humour than horror, missing the point of this bleakly dystopian vision altogether. The nirvana concepts of Before Life and After also didn't hit home; and so we all found ourselves discussing the string quartet as we walked out into the summer night.