Clouds hang thick over Sydney's Manning Bar, where appropriately thick, fast and heavy tunes are about to be unleashed.

Bird's Robe formed over 15 years ago to promote progressive and experimental music across the globe.

From Caspian to Chelsea Wolfe to sleepmakeswaves, Bird's Robe has brought unusual sounds to many longing eardrums, so it was only fitting for some of those sound-makers to celebrate the birthday milestone together (7 December).

The Orphaned Bee sting off the day in style, with a writhing set that can take you anywhere at any moment. Hence Confetti follow, their palette thick and heavy, as they thrash through their strings and your eardrums.

It's a luscious sound that hangs over the audience, pressing down with the weight of 1,000 notes. The drumming is outstanding.

Then clayhands enter with a gentle immersion of sound featuring saxophone and tinkling keys. The piece dramatically shifts into discordance, ending in a running rhythm and weighty sound that feels unfinished, just how it should be.

The keys continue a sad dance before the music merges into a melancholic jive. The second piece builds into a glorious dream of sound, taking you away from any conceivable notion of a worry.

Drummer Heather Darvey expertly builds the momentum into a full release – clayhands have to be experienced to understand how good they are. You are forever changed.

Mowgli is up next, beginning with the lead singer's moody tone as he strums his black Fender. They are perfectly timed as the frontman gives his all on vocals.

The drumming shines again in a fast section. "This song is about how much I love my wife," the singer smiles at the bassist. "This is our love song," she confirms.

Kodiak Empire are straight out of the blocks at a million miles with their post metal, the vocals smooth and strong before the second vocalist screams into the mic. The music twists and turns, each bar a new step of the journey. It's thrilling.

Treebeard are up next, and the moshing is instantaneous. They are explosive, the axe players head-banging in unison. The lights turn kaleidoscopic pink and orange, flashing over the band's ferocity. They mix reverbed sweetness well with the heavier sections.

Squat Club enter with an almost country tinge, the bouzouki player fretting along. The set initially ebbs and flows with a warm intensity, until sharp stabs interject, flowing into a volcano of sound that doesn't let up. It's glorious intensity.

Anubis serve a softer edge, the vocalist bending notes in a Jeff Buckley manner, as the songs crash and tear at your heartstrings. Toehider continue a stacked line-up with one of the greatest displays of musical talent ever to set foot on a stage.

Mainman Michael Mills displays a vocal and guitar prowess that is yet to be seen anywhere else in the world, skating through note sections faster than a bullet train, all while singing high hair metal notes that the greats would dream of.

Hopefully we see Toehider on the biggest stages very soon. "Mike's brought us all together," Mills thanks Bird's Robe founder Mike Solo. "All the weirdos all the freaks," he smiles. Boy are we glad Solo did.

Closure in Moscow keep things rolling with their tight sound and crashing cymbals. Frontman Mansur Zennelli uses a voice double down an octane for interesting effect. The songs are grand and energetic.

Caspian enter gently with ambient swirls before erupting into trilling guitar and rumbling rhythms under the red lights. The sound is overwhelming and euphoric all in one.

The mammoth day draws to its conclusion with sleepmakeswaves. The scale of the sound emerging from only a three piece is remarkable. They thrash their golf-hat covered heads in unison and release more joy for the packed crowd.

A huge day to celebrate a huge promoter of quality music, cheers to Bird's Robe having another incredible 15 years and more.