Initially obscure (with various sound effects and jazzy percussion) and shifting with delicate, layered vocals, Ty Segall’s “Ice Plant” is a “fever dream of my childhood,” he says. The majority of the song (from his forthcoming album First Taste) is occupied by Segall and Lay’s a cappella vocals—a far cry from the previous fuzzy, psychedelic, garage rock tracks from the record. It all floats along …