Mumford & Sons, “Delta” (Island Records)- The Mumfords’ early output had an infectious folksy charm which may have enraged the purists but did prove hugely successful in terms of solid record sales , bringing the band chart-topping albums on both sides of the Atlantic. The passage of time has seen their albums grow increasingly anondyne and predictable however, and the spurious rustic bonhomie which dominated those early offerings has sadly given way to the undemanding melodic balladry which dominates “Delta.” “Darkness Visible” provides a welcome respite from this formulaic fare, delivering Americana artist Gill Landry’s spoken word extract from Milton’s epic poem “Paradise Lost” over a deliciously sepulchral musical backdrop.