If there are two sounds that encapsulate Pixies for me they'd be Frank Black's feral screams on "Tame", and Kim Deal's ethereal vocals on this track.
"Hey", the thirteenth (thirteenth!) song, of the fifteen on 1989's "Doolittle" album, is a bizarre blend of love song and grotesque vignette, in a similar vein to "Catcus" from the previous year's "Surfer Rosa". Like "Cactus", "Hey" combines longing and depravity in equal measure and wraps them up with a wonderful yet simple bass walk from Deal, and Santiago's trademark twangy guitar.
It is, however, the layered, pained cries of "Chained!" from Black supported by Kim Deal's quiet backing that make this song such a classic.