Created by Celer (Will Long) and Machinefabriek (Rutger Zuydervelt) in Tokyo and Rotterdam in June 2012, Hei / Sou brings to a close the duo’s trilogy of seven-inch collaborations. As with the two previous singles, Maastunnel / Mt. Mitake and Numa / Penarie, the release comes with two videos by Marco Douma and is available in a physical edition of 250 numbered copies (downloads also are available of all three releases).

The single’s two pieces are detail-packed microcosms of ambient-drone activity. “Hei” begins with ringing cymbal accents that are quickly joined by burbling synthesizers and electronic atmospheres before the material decompresses to form a becalmed, slow-motion stream of glittering flourishes. Slightly more sedate by comparison, “Sou” scatters micro-flickers of percussive rattlings alongside a central drone until swirls threaten to combust during the piece’s late stages. The video for “Hei” shows an uninterrupted flow of hazy images of sunlight and shadow, with the setting (or rising) sun bleeding through abstract silhouettes formed by what appear to be trees and fences. The treatment for “Sou” adopts a more abstract character, with nary a real-world element displayed within Douma’s blurred scrim of silvery textures and criss-crossing patterns.

One of the most appealing things about the Celer-Machinefabriek collaboration is that it brings out compelling sides of both participants and broadens out their respective sound-worlds in surprising and unexpected manner. Given that each of the singles totals about ten minutes in duration, one imagines that a full-length CD document of the collaborative project might conceivably pair the three singles with a half-hour piece taken from their live concerts. Regardless, it’d be a shame to see such a fruitful collaboration come to an end with the release of this third single.