This essay asks what archival sound objects—in this case a vast stockpile of bootleg music recordings—can tell us about cultures of listening and the cultivation of intimacy through sound under state socialism. It combines ethnographic and historical methodologies to analyze a format for popular music that circulated through an alternative economy in the People's Republic of Poland from the 1950s through the 1980s: the “sound postcard” (pocztówka dźwiękowa). These flimsy, often colorful, plastic rectangles contained copies of mainstream western, Polish, and Soviet popular musics on seven-minute records, sold hand-to-hand at markets and kiosks. In the twenty-first century, these polyethylene flexidiscs circulate as socialist ephemera with a nostalgic thrill, cherished for their obsolescence and provocative visual design reconstruct, but dismissed as poor fidelity transfers. I treat this archive as material history that contains aural traces allowing us to access socialities, affective experiences, and labor relations.