Mark Harrison and his very capable band (whose members include the extremely talented duo Josienne Clarke and Ben Walker) play a curiously English take on American roots music. Their stylistic materials mine the cracks between country blues and old time country music, continuing a UK tradition that began with skiffle and was nourished by the likes of Ramblin’ Jack Elliot and the pop-jug-band sounds of Canned Heat. There’s a sense when listening to American performers in such styles, particularly the older ones, that they are singing from beneath a heavy encrustation of …