Being able to carry around curated music to listen to on-the-go is so significant that innovations in portable tunes have a way of looming large in its era’s zeitgeist.

The advent of cassette tapes made creating custom mixes possible, and then in 1979, Sony’s Walkman introduced the world to carrying and listening to your tracks anywhere. In the subsequent four decades, the cassette tape has been superseded as the preferred portable media several times over, but the plastic cassette case endures as a symbol of carefully crafted and uniquely personal music.