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Lünenburg Heath is a vast, moorland-like tract in northwest Germany, between Hamburg, Hanover, and Bremen. Its low-growing vegetation, gnarled shrubs, and dry soil form the scar tissue left by medieval deforestation. SS leader Heinrich Himmler was secretly buried there. And despite its springtime swatches of wildflowers and family-friendly theme parks, it is a landscape whose beauty stems from its air of desolation.

"Don't get lost on Lünenburg Heath," intones Brian Eno in a nursery rhyme monotone atop a cortège of synth chords. They are the only words sung on Tracks and Traces, a 1997 Rykodisc reissue of a 1976 collaborative recording session between Eno and Harmonia, the veritable '70s German supergroup composed of Neu! guitarist Michael Rother and kosmiche godfathers Cluster.

I have always pinned Cluster as the dark stars in the krautrock universe, based on the drifting, feverish, synthesizer-rich improvisations of core duo Hans-Joachim Roedelius and Dieter Moebius. So I can easily imagine their protean music whistling across Lünenburg at dusk, haunting the ears of daytrippers — a strange and seductive admixture of sprightly pop and forlorn ambient improv reflecting the landscape's more recent transformations and less-than-sunny history.

Having regrouped in 1997 after a decade-long hiatus from working together, Moebius and Roedelius are once again touching down for a rare series of US dates, including a May 23 trancefest at Henry Miller Library in Big Sur and a May 25 show at the Great American Music Hall in San Francisco. And despite Eno's cryptic warning, it's hard not to lose one's way amid the hazy vistas and plaintive melodies of Cluster's music.

Their expansive discography — which includes a recombinant cast of regular, notable collaborators such as Eno, Can bassist Holgar Czukay, and überproducer Conny Plank — provides a few signposts. Roedelius and Moebius initially teamed up with fellow electronic musician Conrad Schnitzler in 1969 as Kluster, releasing three explosive documents of improvisation that rapaciously incorporated elements of 20th-century classical music, jazz, and rock. Important Records' recent release, Vulcano: Live in Wuppertal 1971, paints a vivid picture of this early period.

Schnitzler left the group in '71, taking the hard "k" with him. From then on, Cluster recalibrated its keyboards toward a more subdued and, at times, even pretty and poppy aesthetic. Improvisational jams gave way to shorter songs, and the lurking menace of 1972's Cluster 2 (Brain/Water) was followed by the double about-face of drum machine confections on Zuckerzeit (Brain/Lilith, 1975) and the pastoral miniatures of Soweisoso (Sky/Captain Trip, 1976).

Still, dark patches are a consistent hallmark of Cluster's terrain, even when they choose to let the sun shine through. The superficial pleasantness of their two collaborations with Eno released at the time, 1977's Cluster & Eno (Sky/Water) and 1978's After the Heat (Gyroscope), belies the affective force — what could be described as a low-simmering melancholy — of certain songs. The slow progression of blue notes that form the woozy melody of "Für Luise," from Cluster & Eno, linger long after they have decayed into the Gershwin-like piano of "Mit Simaen." Cluster & Eno's cover photo returns us to a field — though not Lünenburg. A lone microphone stands at attention against a faint mother-of-pearl sky, which ends at the smudge of shadowy foliage at the bottom of the frame. It's near twilight. Cryptic and evocative, meditative and inexplicably sad, the image provides a visual analog to Cluster's chimerical output.