apanese label Headz draws its name indirectly from James Lavelle’s indie blueprint Mo Wax and its namesake compilation. Indirectly, because in Japan, Headz has developed into a genre signifying just about anything left of centre: indie-electronics, offbeat, weird or just instrumental hip-hop, right through to post-rock. It’s all Headz.

The Japanese are amazing at cataloguing. Trends, fashion, fads, arts, and especially music. A lifetime’s worth of record shopping won’t find you records you can find right now in havens like Warzawa, Vinyl, Cisco; even HMV and Tower are fantastic in Tokyo. And it was flipping through listening stations at HMV, Shibuya that I first found these two discs.

The question I ask with Japanese music is: Is this original and special or well crafted and copied? All too often it’s the latter, no more than a cute, capable recreation of music from elsewhere (Kyoto Jazz Massive, Shonen Knife). Of course, there are plenty of the former too (Cornelius, Afrirampo, Merzbow, Tujiko Noriko, Aki Onda, Krush). Is it good enough to sound lovely or do you need to be original? Devoid of the emotional payload of lyrics, it’s difficult to make a call about musical quality. Especially in music as intangible and deliberately chameleon-like as post-rock, where even Tortoise face routine criticism for poking around for sounds like shine-struck magpies.

It’s all too easy to compare Sangatsu’s music to the big names of post-rock. Even the band fit the model: three guitarists and two drummers, with programming and field recordings. But turning up the volume exposes surprising depth. A single plucked guitar opens the album Still Life. The sound is sustained, dragged out; it seems to be operating in geological time. Field recordings are interleaved into the guitar notes, trains moving through a station, low chatter, and the hum of, what?, a wash of noise that could be a distorted stereo or wind outside the window, except that it abruptly cuts out every so often as to remind you that it’s not incidental.

Tortoise is a big influence on the quintet, of course. The elegant guitar lines hark back to the past couple of Sonic Youth albums too, the melodies shimmer over drum rhythms taut as stretched rope. It’s pretty, though it takes a few tracks for Sim to get into their own sound. Gradually the sweet sounds are coupled with threatening noise and heavy thudding double bass. “Night Map” flirts with repetition, looping a single guitar note far past expectation and sharply juxtaposing it against a summery guitar melody and crisp high hats.

Sim have quite a different sound. It’s closer to a Mike Patton freak-out rock track played by a laptop head with a background in sound art and jungle, but without the cathartic release of any of those. And that’s just the first track. Internet ‘handshakes,’ post-rock guitars, and loose drums start second track “Split.” It features vocals that go uncredited—are they found samples or does no one want to take credit?—whatever, the flat spoken words are stripped of meaning by heavy processing (it’s hard to tell if it’s Japanese or English, frankly). Like German group Tarwater, the vocals completely change the musical dynamic.

As the trio progress through their taxonomically Autechre-influenced tracks (“db23,” “dok,” “w”), they keep experimenting with the dynamics of their sound—drum rolls, pianos that play little melodies and then suddenly stop, bass guitar thwacks. However, it’s when the record takes a belated stab at rhythm on second last track “Rec” that they really click. A looped beat plays a jackhammer techno in the background, like a skipping CD caught on a single beat.