"Well" deadpans Zeal & Ardor frontman Manuel Gagneux midway through their set "Heriot are an angry band aren’t they!”. He goes on to admit that that anger means his band have had to up their game every night to keep up the ferocity of these fast-rising youngsters. Heriot are fuelled by rage, but it is not indignant or nihilistic fury. Theirs is peppered with passion and exasperation. They manage to perfectly personify the generation Z view of the world that they are inheriting. They are not despondent, they are incensed and, more importantly, they are motivated, and they are invigorated.

Musically they manage to effectively fuse the seemingly incompatible worlds of prog and hardcore. They are loud, they are caustic, they are brittle, but they also possess real depth and resonation. You don't achieve their intriguing and complex coarse texture by just simply crashing around on your instruments. Instead, there is a lot of intricate construction going on here, layers of dense sound sandwiched together to create a wrathful cacophony.

They are also a band finding both their feet and their voice. I have been fortunate enough to catch them multiple times over the last year in multiple support slots and each time there's been an evident leap in their maturity. Being able to witness a young fledgling act blossom in front of your very eyes is very much the joy in what my fellow scribes and myself choose to do. Rough edges and incendiary irritation will always be an essential part of Heriot’s sound. What has changed is that they are learning how to effectively channel and express that. I wait with bated breath for our next meeting.

It is obvious from the start of Zeal & Ardor’s set that something is missing. That's something is backing vocalists Dennis Wagner and Mark Obrist. They usually flank Manuel on either side of the stage, creating an impenetrable wall of vocal dexterity, but tonight they are conspicuous by their absence. We are five songs in before Manuel decides to tackle the elephant in the room and introduces the band as a "percentage" of Zeal & Ardor. It is revealed that both Dennis and Mark are sick, and the quintessential part of the band’s unique sound that they usually provide instead comes via backing tapes and, increasingly as the night precedes, the audience themselves. There are two unexpected consequences of them being AWOL. The first is that it allows the listener to fully gauge and appreciate the astounding range that Manuel himself possesses. As stated, there are tapes to back him up, but he certainly steps up to the mark this evening and takes on much more of the vocal heavy lifting than he usually would. Watching him effortlessly switch from abrasive howls to deep soulful intone is quite staggering.

The second silver lining that comes from having a depleted line-up is that it allows the musicianship Tiziano Volante and Lukas Kurmann to shine out. Zeal & Ardor are a vocal-led outfit and usually, it is the power trio of Dennis, Mark and Manuel that monopolise the spotlight. With a gap on both his left and right side, Manuel is given the opportunity to playfully duel and interact with his fellow musicians in a way that I've not seen before. The simplicity but simultaneous power and clout of their musical offer also really comes to the fore. The riffs are short, sharp and driving. They exist to provide a rhythmic perpetual motion that the vocals can be layered on top of. This evening I become acutely aware of how impressive their precise minimalism actually is. There are no ornate trappings, instead the pulsating tones are precision engineered to do no more and no less than the job in hand. No waste, no warbling but utterly exquisite.

What is astonishing about Zeal & Ardor is their ability to be completely unique while concurrently overtly familiar. There are times when they are very black metal and there are times when they sound distinctly like Rammstein, BUT the vocal approach is simply unlike anything else in our world. We are used to our music being driven by the guitar. They have completely turned this on the head and instead, it is the vocals (usually supplied by three sumptuous voices) that create the urgency and the momentum. It takes everything back to the raw components that rock 'n' roll was built upon and it is exhilarating.

The fevered response that they receive tonight shows that they have gone well beyond being a novelty act and instead they have invigorated and intoxicated a growing audience. They are treated with reverential adoration from start to finish. Quite simply they are the most exciting thing to happen to metal in decades and the fact that three albums in they are still finding new ways in which to be astounding is pretty miraculous. The problem with most new approaches is that they quickly become pedestrian and de-rigeur. Zeal & Ardor have managed to achieve the unachievable in the fact that they're fresh and exciting take on our tried and tested genre continues to be fresh and exciting six years on from their extraordinary debut album. Every time I am blessed with seeing them live, I fall in love all over again with what they are doing, and tonight was no exception.

Check the “In The Flesh” page for more photos! Zeal & Ardor, Heriot