The origins of “Walk The Line” come from playing Bavarian guitar music backwards.
When Johnny Cash was in the air force he found solace and pleasure in playing guitar and writing songs, but in an interview with Larry King he explained that the prominent shuffling sound that runs throughout “Walk The Line” was inspired by the sound of a tape playing backwards. Even more amusingly, it was actually a tape of Bavarian guitar music. Johnny explained:
Oh. I had a little recorder. I had a Wilcox Gay Recorder — a tape recorder in the Air Force in 1952. And I was always — only guitar I was going do-do-do-do-do — well it got turned around. The tape got in there backwards. And hen I played it, it went sh-sh-sh-sh and it had a kind of a drone sound like I finally had on the record.
But I couldn’t figure out where that sound came from when I played it. When I took that sound — when I got home — when I was home from the Air Force, I was on the road and that sound was haunting me again. And then— but then the line “because you’re mine, I walk the line.” It kept coming to me, you know?