Both recorded versions of "Cross Road Blues" demonstrate Johnson's crooning, crushing singing style and fearsome guitar skills, still imitated by blues and rock n' roll musicians to this day.
Spin Magazine, Rolling Stone, and Guitar.com have all granted Johnson posthumous ratings as one of the greatest guitar players of all time. Bob Dylan, Keith Richards, Muddy Waters, Jimi Hendrix, and Eric Clapton are some of the more famous names to spend their lives trying to emulate Robert Johnson. Clapton is the most intense about it: after he heard Johnson, he says, "I realized that, on some level, I had found the master, and that following this man's example would be my life's work."
But unless you are a pre-seasoned blues buff, the reason for all the hype can be hard to hear in the simple recordings that make up Johnson's tiny oeuvre. But Clapton explains it well: Johnson is "simultaneously playing a disjointed bass line on the low strings, rhythm on the middle strings, and lead on the treble strings while singing at the same time." Or, in the words of a less exacting critic, "When you get to 'Crossroads' …oh my God, forget it. It sounds like three guys playing." In other words, the sound is simple, but the technique is incredibly difficult to learn.
"Cross Road Blues" really does sound like it could be three guitars playing. In its simple brilliance, the song has all the typical features of a Robert Johnson tune. The guitar is tuned in open A tuning, which allows him to use a slide (usually a glass "bottleneck" slide in those days) on the open strings. As he riffs on the slide on the high strings, he's strumming the "dun-ta-dun-ta" sound known as the boogie shuffle. The boogie sound is now an easily recognizable signature of blues music. Although he didn't come up with it himself, Johnson's recordings have become classic, and "Cross Road Blues" demonstrates the early use of the common boogie sound. You'll also note that while the song is mostly in 4/4 time, Johnson is not afraid to throw in a 5/4 measure or two for the sake of his quavering guitar solos, another typical element of his creativity.
As for the singing, a webpage about how to play like Robert Johnson advises that you "gotta sing like you've got hellhounds on your trail." Another commentator says Johnson sounds "like he's about five minutes away from the electric chair." Even if you don't believe in possession by the devil, there's something guttural and desperate about the singing that captivates people and that few have been able to imitate.