By chance or design, the latest entry in the kracfive.com collective’s monthly “MP3 rotor” of free downloads clocks in at three minutes and 33 seconds, which means it makes you picture a spinning chunk of vinyl even before you enter its scratchy little sonic world, in which an LP’s surface noise clip-clops like a sodden horse and voices echo past like a lo-fi poltergeist, all edited and sequenced to maximize the sense of moldy continuity. The song is “Atomsk” (MP3) by Octopus Inc. and Le Gun, who have found a unique way to share credit: in the file name, Octopus gets listed first, but in the MP3 file’s artist tag, Le Gun gets top billing. There’s a point about a minute in that exemplifies their ace sense of timing, when the whole thing takes a deep breath of space for all of about a tenth of a second, before rebooting. The looped guitar, the distant squawks, the hoarse whistles — “Atomsk” has all this and more, packed tight as a suitcase. Check it out at kracfive.com.