It's 10.30 on Friday night in Galway, the West of Ireland city that is hoping to become the country's next European Capital of Culture, and down-town Quay Street is buzzing with noisy life. Given the array of bars and restaurants dotted along the narrow street, this isn't unusual, but as it is the first weekend of the 2015 Galway International Arts Festival, an annual two-week melee of theatre, music, art, comedy and spectacle that styles itself as "The Festival of Extraordinary Experiences", the vibe is different.

Sure enough, the sound of martial drums in the distance attracts revellers onto the street, where the crowds part as three gigantic frock-like constructions are wheeled by, with the white-painted faces and torsos of a trio of opera singers at the centre of each. As they pause every few hundred yards or so, flanked by the equally colourful Tin Soldiers' Band of Drummers, the singers of The Giant Divas and Les Tambours regale the throng with excerpts from Carmen and an Edith Piaf number before moving off again.

As extraordinary experiences go, French street theatre company Transe Express's latest outing into the international festival circuit, following appearances at Sydney Harbour, the London Olympics and several turns during Edinburgh's Hogmanay programme dating back to the 1990s, is the perfect larger-than-life weekend serenade.

It is also indicative of the spirit of Galway International Arts Festival, which, under the guidance of Paul Fahy, its director of the last ten years, has developed an already expansive programme even further. This mix of subversive populism can in part be defined by Australian artist Patricia Piccinini, who took her seventy-foot tall missing link she calls Skywhale to the air in the form of a hot air balloon. Skywhale's cartoon-like enormity captured a collective imagination in a way that made audiences flock to Relativity, Piccinini's exhibition of similarly moulded mutant creatures at the city's temporary Festival Gallery, set in an old print-works.

An unsettling mixture of cuteness and a form of anthropology culled from science-fiction, Relativity's uber-real looking sculptures offer up a world of possibilities as fantastical as GIAF itself. Only an unseasonal outbreak of high winds managed to ground Skywhale, and even then only temporarily. This may have had something to do with former Split Enz singer Tim Finn encoring with Weather With You, the hit single he co-wrote for Crowded House with his brother Neil, at the end of the first of two nights performing in St Nicholas' Church.

Weather With You and Split Enz's Six Months in a Leaky Boat, which he performed on the second night, were the nearest Finn came to greatest hits during White Cloud, an intimate and deeply personal mix of song, spoken-word and home movie footage that explored Finn's roots in New Zealand. While making for an at times raw experience as Finn sang with only piano and guitar accompaniment, White Cloud was a moving piece of multi-media storytelling that wouldn't look out of place in Irishman Fergus Linehan's eclectic inaugural programme for Edinburgh International Festival, which starts next month.

There are numerous connections between Galway and Edinburgh, both in current and past programmes. It was at the 1997 GIAF where Enda Walsh's career-making play, Disco Pigs, starring a nineteen year old Cillian Murphy in his first professional job, played to acclaim before Corcadorca company's ferocious production took the world by storm following its Edinburgh Festival Fringe run.

Walsh has continued his connection with GIAF, with the festival co-producing Ballyturk, Walsh's 2014 play that reunited him with Murphy prior to the show transferring to Cork and London. Also in the Ballyturk cast was Mikel Murfi, who will be appearing in The Last Hotel, Walsh's forthcoming opera which premieres at this year's EIF.

This year's GIAF saw Walsh open A Girl's Bedroom, the second of what looks set to be an ongoing series of new texts presented as installations in a gallery setting designed by Fahy. With an audience of five led into Fahy's pink-perfect recreation of a six year old's room, the lights dim as the recorded voice of actress Charlie Murphy recounts a twelve-minute psychodrama about a woman who carries every detail of her past around with her. In tone it resembles Tennessee Williams' miniature masterpiece, Talk to Me Like the Rain and Let Me Listen, and, delivered in Murphy's hushed tones, is similarly evocative of a life erased.

One of the major successes of the 2014 Edinburgh Festival Fringe was riverrun, Olwen Fouere's startling dramatisation of sections from James Joyce's novel, Ulysses, for which this most singular of performers won a much deserved Herald Archangel, an honour previously bestowed upon Walsh. This year at GIAF, Fouere was performing Lessness, a staging of an experimental short story by Samuel Beckett inspired by composer John Cage. Like riverrun, Lessness was co-produced by GIAF, an initiative which has been developed during Fahy's tenure so that much of the festival's main programme sees it receiving a producer or co-producer's credit.

This was the case with both Amy Conroy's Luck Just Kissed You Hello, and a revival of Frank McGuinness' startling play, The Match Box. Conroy played the lead in her study of siblings at war with each other as their father lies dying, in Caitriona McLaughlin's production initiated by the HotForTheatre company, and rising star Cathy Belton gave an equally astonishing turn in Joan Sheehy's production of McGuinness' play. Conroy put humour to the fore in a study of how family defines us, even as her character Laura returns home, reinvented as Mark. As s/he enters the man's world of her brothers, the roots of all their dysfunctions begin to show as an everyday emancipation takes place.

A family is ripped apart in dramatically different fashion in The Match Box, in which Belton plays Sal, a woman on the run from herself as much as others as she relates her fate in an isolated country cottage. As she talks of a loss that gives vent to a rage worthy of Greek tragedy, Sal becomes emotionally and physically more brittle, striking matches as she goes, watching the flame of life burn quickly in a searingly powerful piece of work.

Visiting shows included Exhibit B, Brett Bailey's searing meditation on racism that was pulled from its London dates following protests last year after its EIF run. While the show went on in Galway without incident - as was the case in Edinburgh - Bailey's depiction of racist atrocities using live performers in a series of tableaux vivants left audiences who saw it similarly stunned and discomforted.

A music programme featured a series of programmes by the RTE National Symphony Orchestra and a series of traditional showcases, including the duo of fiddler Brid Harper and guitarist and whistle player PJ McDonald, who played a packed-out Saturday afternoon session in Monroe's Live venue.

On the banks of the River Corrib, meanwhile, the giant blue Festival Big Top held court to large-scale concerts by St Vincent, Damien Rice and John Grant, the latter of whom was upgraded to top of the bill after Sinead O'Connor was forced to withdraw through illness. O'Connor missed some of the biblical weather that caused some performances of outdoor shows such as the high-flying Turned Upside Down and Man on the Moon to be rained off, though that didn't bother the four thousand revellers watching Irish band Kodaline inside the Festival Big Top.

Nor did it bother the Giant Divas, who paraded through the streets a second time sporting mini umbrellas attached to their heads. By Sunday teatime, even Piccinini's Skywhale was airborne once more, providing a whale's eye view that showed just how extraordinary Galway International Arts Festival can be.

Galway International Arts Festival 2016 runs from July 11-24. www.giaf.ie