A lot of big-ticket concerts were announced this week, including Built to Spill's four-night celebration of their 1999 album Keep It Like a Secret at the Doug Fir on October 30-November 2, and the Black Keys, Modest Mouse, and Shannon and the Clams hitting Moda Center on November 22. But the single most exciting ticket that went on sale this week is for a show featuring an obscure Swedish psychedelic band whose name I'm not entirely sure how to say out loud.

Träd, Gräs och Stenar (it means Trees, Grass, and Stone) was a legendary band on the Swedish progg scene, and they played freeform psychedelic pagan jams that sound like continents banging into each other. Their name was mostly a whisper on the lips of record nerds for decades until their legendary stuff was reissued in recent years, alongside records from the band's earlier incarnations Parson Sound and International Harvester (later shortened to Harvester).

After disbanding in the early '70s, Träd, Gräs och Stenar reformed several times in subsequent years. They played Berbati's Pan in 2004, opening for Stephen Malkmus and the Jicks. Now they're returning to Portland 15 years later, for a show at the Liquor Store on Tuesday, April 23. The current incarnation features Jakob Sjöholm, who joined TGS in '71 and was part of the Harvester collective, and guitarist Reine Fiske of Dungen. Last year, the band toured under the altered name Träden, although it remains to be seen if this current jaunt, under the band's original name, is anything more than a pragmatic shift to the more familiar nomenclature. So far, the group is also hitting Seattle's Sunset Tavern (April 24), the Marfa Myths festival in Marfa, Texas (April 27), and Rough Trade in New York City (April 29), although a full tour has not yet been announced.

Träd, Gräs och Stenar's music is wild, freeform, and deliberately unpolished (most of their old recordings are decidedly lo-fi), and very much in communion with the so-called "hippie" ideal of earth-based living, although it's so different from what most Americans imagine that music to sound like (namely, the drug-slicked grooves of the Grateful Dead and Phish) that it'll probably alienate most jam-band fans. For seekers of far-out sounds and music-as-ritual transcendence, though, Träd, Gras och Stenar are ground zero. Tickets for the Portland show went on sale yesterday and are almost certain to sell out.Cop your entry to this historic event here.