Radiohead, 2000. The follow-up that retreated from rock into electronic abstraction. The defining 21st-century rock album.
From Wikipedia
Kid A is the fourth studio album by the English rock band Radiohead, released on 2 October 2000 by Parlophone. It was recorded with their producer, Nigel Godrich, in Paris, Copenhagen, Gloucestershire and Oxfordshire. Departing from their earlier sound, Radiohead incorporated influences from electronic music, krautrock, jazz and 20th-century classical music, with a wider range of instruments and effects. The singer, Thom Yorke, wrote abstract lyrics, cutting up phrases and assembling them at random.