Intermezzo's annual summer concert at St John the Evangelist offered audience members an escape from the UK's recent heat wave to the colder climes of Scandinavia and the Baltics. The choir has gone from strength to strength in recent years, tackling a range of 20th- and 21st-century works by lesser-known composers alongside more popular choices.

The encircling overtones that marked the start of the concert made it clear that this was a choir with skill and confidence. Sitting in the centre of the nave, conductor Andrew Ker led the choir's synchronised voices through Augustinas' Anoj Pusej Dunojelio with the nostalgia of a final return home. What stood out was the conductor's complete trust in his choir, safe in the knowledge that with the smallest of gestures the sound would grow and stop in unison, despite the unconventional staging.

Ešenvald's The Heavens' Flock required a choir that sang as one with the voices of many, and Intermezzo certainly did just that. One of the group's strongest assets is its balance, constantly shifting by slight increments to maintain clarity.

The intonation of the shimmering vocal trills that began Dubra's Stetit Angelus was not without issues, but the effect of the incense clouds and sparkling gold was nevertheless effective. The real display of skill came in the ending – the well-handled building of the final chord alongside the sounds of the smoking incense to a great crescendo before dying away.

Pärt's Which Was the Son of..., a list of names in the Icelandic patronymic tradition, was rather like a sung version of the phonebook, done with technical skill and an energy that made it more engaging than the lyrics may have otherwise suggested.

In a programme of music from Scandinavia and the Baltics, Whitacre's When David Heard seemed to bear no resemblance, but the idea of sons taken from the Pärt meant that the Whitacre felt more like a permissible tangent. Ker's pauses between phrases allowed the sound to reverberate around the building but halted the emotional intensity of the stuttering grief-filled repetitions of the lyrics. However, what the choir lacked in acting here they made up for in musicality at the emotional climax – a moment where I was not alone in fighting back the tears.

Voices, chimes and wine glasses blended seamlessly in Ešenvald's Northern Lights, and the sense of awe and energy was sustained at a remarkable level throughout. In the excitement, the wine glasses were hard to hear at times, but the piece's quiet conclusion of held chords, chimes and wine glasses really showed off the unusual instrumentation and the choir's versatility.

Dubra's Laudete offered a moment of light relief as a shorter piece for female voices. In a more exposed setting, the real sense of joy on some of the singers' faces was what brought the piece to life.

Calm descended on the audience during Pärt's The Deer's Cry, another piece sung by a small group with excellent synchronisation and tantalising unresolved chording.

The chromatic harmonies of Miškini's O sacrum convivium showed an adept handling of the more complex lines. While the slower sections seemed full of languorous enjoyment of the harmonies, the speed of the faster sections left the lyrics behind at times.

Sandström's Biegge Luohte set the choir on a lively trajectory towards the concert's conclusion. From the opening fanfare calls to the leaping solos around the choir to the whistles of arctic birds and the percussive dog yaps, the driving energy pulsed throughout the choir from beginning to end.

The sidestep from Sami mountains to Scottish heaths in Mäntyjärvi's Double, Double Toil and Trouble maintained the frenetic supernatural feel and saw the choir really engaging with the text they were singing and performing; the conviction in the spoken sections wouldn't have been out of place in an acting company. With witchiness from beginning to end and frenzied rhythmic complexities, the earthquake-like stamp in perfect unison saw more than one audience member momentarily take flight.

We were treated to an encore; the result of extensive applause at previous concerts, and this was no exception. In Lukaszewski's Crucem tuam adoramus the choir sang with a palpable feeling of warmth in their voices and a sense that this was a choir that truly loved singing together – a welcome thawing after the programme's colder setting.

Overall, the concert was a great feat of musicality and showed just why Intermezzo is seen as one of Oxford's best amateur choirs. Any slips or flaws were soon forgotten in the breath-taking climactic moments when the group pitched it just right.