On their sixth album, Foo Fighters have renewed their membership in the "if it ain't broke . . ." school of songwriting. And essentially, there's nothing wrong with that. "Echoes" hosts plenty of the Foos' usual soft-louder-loudest "radio friendly unit shifters" (to borrow a phrase from frontman Dave Grohl's old band): Lead single "The Pretender" and "Let It Die" start with near-whispers before kicking into giddily catchy, fuzz box-driven hollered hooks, while "Erase/ Replace" chugs with shouts and power chords from the top. Amid a brace of undifferentiated midtempo rockers and a couple of quieter pieces (hence "Echoes, Silence . . ."), the only truly disappointing track is the treacly strings-and-piano closer, "Home." Meanwhile, the brooding, melodic "Stranger Things Have Happened" and "Summers End" stand out for their delicious sundown grooves.—Jessica Letkemann