Animal Collective are one of the 21st century’s most distinctive acts, and one of the most experimental to find widespread success. Yet their transition from tribal freak-outs at Brooklyn art spaces to packing out auditoriums was by no means preordained.

Several factors contributed to their success. An open-door policy for the four band members – Josh Dibb (Deakin), Brian Weitz (Geologist), Dave Portner (Avey Tare) and Noah Lennox (Panda Bear) – and the freedoms afforded by a supportive, tight-knit scene let the band develop with minimal pressures. This resulted in a divergent, genre-agnostic discography: Seven full-lengths arrived in seven years, each bringing a newly curious set of fans, who would interact at length with the group on web forum Collected Animals.

Such nonlinearity became a running trend for Animal Collective, forging the group’s reputation as low-key custodians of weird sounds. Release by release, concert attendance swelled in tandem with growing critical clamour. By the mid-to late 2000s, they were finding their way onto the bills of large European music festivals like Reading and Primavera, while drawing national press coverage in the States.

2009’s Merriweather Post Pavilion was a full-bodied realisation of their potential. Synergising elements of the records that preceded it – the immediacy of Sung Tongs, reflecting-pool shimmer of Feels and jittery euphoria of Strawberry Jam, as well as the beatific sample kaleidoscope of Panda Bear’s influential solo effort Person Pitch – it was a generous listen, crackling with newfound warmth and open possibilities. While continuing to expand their dense tangle of sound farther out into electronic territory, Merriweather was simultaneously an articulation of what lay in reach. Lyrically, it grappled with life and death in close family, and reflected on the fading freedoms of adulthood.

This marriage of motifs struck a chord with fans and critics alike. It was widely heralded as a high-water mark for left-of-the-dial music, breaking the band into completely new territory. Its breakout can be attributed as much to a fortuitous quirk of timing as the album’s exceptional quality: indie rock, dominant for much of the ’00s, was peaking, and Merriweather seemed to signpost the sounds (alternative pop, colourful house and techno, overlapping puddles of post-internet electronica) of a new decade to come.

Of all their releases, Merriweather presented the then-trio’s collage of influences to the masses in a manner that felt truest to their origin. Listeners could seek out what they wanted from it: Some heard Beach Boys, others heard Gas. Not for nothing does it simultaneously rank in Groove’s best electronic releases of 1988-2013, and aggregator site Acclaimed Music’s top ten psychedelic rock albums of all time.

This oral history, drawing on original interviews with all the band members, as well a dozen of additional people close to them, follows the arc of Animal Collective: from their origins and run of exciting and unconventional music across the 2000s to the aftermath of an unlikely crossover.