Though it was written in 1956, Johnny Cash's "Folsom Prison Blues" has the sound and feel of a much older song. It's that essential, three-chord, old-timey feel that makes it a natural for the banjo, either as a solo instrument of part of a bluegrass band. The key to Cash's epochal live version of the song is the interplay between Cash and guitarist Luther Perkins. The challenge for the banjo player is capturing the essence of that interplay on a single instrument.
Keep It Simple
Keep your banjo in basic-G tuning (G, D, G, B, D, fifth string to first). "Folsom Prison Blues" benefits from the simplicity of the most popular banjo tuning.
Change chords using barres. "Folsom Prison Blues" is a standard three-chord blues essentially built out of major chords and 7th chords -- G7, C7 and D7, in the case of the basic tuning. The G is sounded by playing all strings open (unfretted); the C is sounded by barreing across all strings five frets up; the D is seven frets up. The 7th is sounded by hammering-on the first string three frets above the open position or barre.
Play a "boom-chik" rhythm by thumbing the bass and grabbing clusters of strings with your thumb and fingers. Alternate this form with a frailing style, where you thumb a bass note and strum up and down across the strings with your fingers.
Take a good listen to the song. It's a slightly unconventional 20-bar blues that starts with eight bars of the tonic followed by four bars of the fifth chord (C), followed by four more bars of the tonic, followed by four bars of the seventh (D), and then back to the tonic for two measures before starting another verse.
Use the banjo as a rhythm instrument during verses. Carry the melody with your voice and use the "boom-chik" style to create a drum-like accompaniment. Keep fills to a minimum during breaks in the singing, but instead keep a one-two rhythm going to propel the song.
Playing the Solo
Play the solo after two verses. Slide up to the 12th fret to replicate Luther Perkins' rockabilly-inspired solo. Play the second string open, then the first string open, the hammer-on the first string two frets up, then pull off, then hammer-on the first string three frets up. Repeat the first-string portion of the solo four more times, double-timing the last two.
Repeat the pattern with slight variations for the remainder of the solo. Move down to the fifth fret and play four bars of the same pattern of notes, varying the rhythm for color. Play four bars open, then move up to the seventh fret and play the same pattern once.
Conclude the solo by playing the fourth string seventh fret (three times), fourth string fifth fret, fourth string third fret and finally fourth string open. Try bending the fourth-string/third-fret note for an even bluesier feel.
Repeat the solo for your outro after you sing the final verse.