The secret to writing a perfect pop song? Learn everything -- then forget it. Just look at Supergrass. This English group, playing Monday, March 17, at the Bluebird Theater, with the Coral, is almost an encyclopedia on tape of British popular music. Even a brief earful of any one of the band's four albums, from 1995's I Should Coco to the just-released Life on Other Planets, will tickle the underside of your pop subconscious. Does it sound like Wings? Stranglers? 10 CC? Soft Boys? Bowie? Well, yeah, exactly. Like acrobats or fighter pilots, the four guys in Supergrass make the whole thing look as effortless as falling through the air. Riffs and harmonies as big and buoyant as blimps are held aloft by lyrics like "You ate our chips and you drank our Coke/And then you showed me Mars through your telescope." The result is often silly...seriously silly. The first song on Life on Other Planets is named "Za" in honor of its nonsense backup lyric; it's sort of like the Faces' "Ooh La La" gummed up with marshmallow. As Squeeze-style piano fluff is spooned over a scoop of Buzzcocksian power pop, singer Gaz Coombes offers up the brilliantly dumb couplet "Time waits for no one/So why don't we get it on?" Easy? Hardly. See the band live, and you'll understand. Supergrass makes its pop-history lesson feel more like a field trip.