What does it mean when a compilation mixes old and new without an exposed seam? The cynical answer wouldn't be too flattering to the new stuff, but it's a little more complicated when the material in question derives from post-punk, the '70s and '80s movement during which punk wormed free from its raw constraints in a way that has found new resonance as a now-sound. The two-disc survey Rough Trade Shops Postpunk 01 serves up lots of canon fodder–Gang Of Four, The Fall, Wire, ESG, Public Image Ltd.–but even its biggest names serve a canon still sketchy enough to bend to new designs. So, how does the old wave sound in light of post-punk's new wave? For starters, the integration of dance elements into heated rock shapes was less literal then than it is now: The thwacky disco simmer and gloriously flat saxophone in Liliput's "Die Matrosen" sound like shifty speculation more than tight formulation. Compare it to "Out Of The Races And Onto The Tracks" by new-school leader The Rapture, and it's clear which was guessed and which was received. The newbies in The Rogers Sisters take their cues well in "Delayed Reaction," a moody, slashing rock roller that treats bass as an integral hook-generator instead of an accent instrument. The era-spanning back-and-forth adds a lot of intrigue to Rough Trade's 44 tracks, but it's just as easy to get lost in the gooey slew of ideas. Blurt's "The Fish Needs A Bike" bleeds a curious form of un-funk from a searing guitar figure that barely changes. Family Fodder charges through reconstructed jangle-pop in the deliriously shifty "Debbie Harry." Contemporary style-miner Gramme shows how much room death-disco has left to chart in "Like You." Duds are mostly nonexistent on Rough Trade, which makes a good game of pitting tracks together to highlight their common divergences. It works to grease down crucial compilation flow, but it also helps pitch history as a living lesson that should be as leading as it is lionized.