Like all Memphis music institutions started in the considerable wake of Sun Records and Elvis Presley, the specter of Elvis hung over Stax: The first version of “Green Onions” was cut on a lathe at Sun Records the same day it was played on the radio and lit up request lines, becoming an unlikely hit. Elvis’ childhood neighbor, Louis Paul, recorded for Stax’s Enterprise imprint. Elvis himself recorded at Stax Records in 1973, cutting a bevy of songs in the middle of the night—when Isaac Hayes often recorded; he was asked to reschedule—in what amounted to the final serious studio sessions of Presley’s career; the songs would form the bulk of his albums from 1973 through 1975. 

But there’s one artifact that chronicles the cultural exchange between Elvis and the legendary labe...