After a six-year hiatus between studio albums, Chicago avant-metal group Pelican makes up for lost time with its tightest, heaviest, and most inventive album to date. Experimenting with metal’s various strains and tensile strengths has been the foursome’s stock-in-trade for nearly 20 years, and Nighttime Stories continues that tradition, packing these eight bracing tracks with crepuscular melodies, gut-rumbling bass, unexpected tempo changes, and a bottomless well of crunchy riffs. From the spectral acoustic guitar that wends its way through opener “WST” to the battering-ram rhythms of “Midnight and Mescaline” to the sludgy title track, their sixth LP balances uncompromising heaviness with surprising poignancy. To wit: The eight-minute closer, “Full Moon, Black Water,” begins as a lurching doomscape that threatens to shake the world apart, but turns at the last minute to rest on a wave of delicate acoustic chords.