It contains songs from all six volumes of the American Recordings release so far, and the Unearthed box-set. I put the Cash covers right after originals, including the songs that he covered himself, like Delia's Gone (though the first Cash recording of this song, which dates from 1962, is not yet on Spotify, the other early version in the compilation Legend sounds different enough to me to be included). For traditional songs like I'll Fly Away, I tried to use the earliest recorded versions available. In the case of Wichita Lineman, though it's first and most famously recorded by Glen Campbell, I think it's more interesting to use the author Jimmy Webb's own recording as the original. I also chose to use Cash's early recordings of Hank Williams songs as the "originals" here, if possible - I assume people who are interested in this playlist already know Hank Williams well enough.
I only kept the songs that I the originals could be found on Spotify, because the aim of this playlist is making it easier to compare the difference between interpretations, if you want to fully appreciate Cash's album on its own, click the album title and listen to it in its entirety. I highly recommend you to do that as well: A Singer of Songs from Unearthed, one of the most moving performance from the Man In Black, is not in this playlist (I don't even know if an original recording exists, is this a song written for Cash?).
Here's the Spotify playlist: Johnny Cash: American Recordings & The Originals (194 tracks, total time: 10 hours) If you find other original songs become available or want to recommend a more suitable version than the one I chose as original recording, please leave a comment. Thanks.