The music of "Subterranean Homesick Blues" can be discussed, oddly, mostly in terms of another song. "Subterranean Homesick Blues" owes much of its sound to the Chuck Berry song "Too Much Monkey Business." Like Berry's song, "Subterranean Homesick Blues" features rapid-fire lyrics spit out over the same blues harmonies and a similar twang of electric guitar licks.
The first lines of "Too Much Monkey Business" are distinct not because of the lyrics themselves but because of how many words Berry crams into a single line. His style is something of a "talking blues" style (which, as the term suggests, consists of speaking over a blues progression). The rhythm is much more important than any idea of melody in this style. The melody of "Too Much Monkey Business" is then, in appropriate fashion, only a single note sung rhythmically like fast-talking. Dylan does the exact same thing in "Subterranean Homesick Blues." While Both Berry and Dylan do change the note they're singing to match the chords, what makes the vocals interesting is the speed and variation of the rhythm in which the words are sung. That fact has led some, like author and professor Camille Paglia, to point out how the "rhythmic ranting" of "Subterranean Homesick Blues" is a sort of bridge between modern-day rap and "agrarian 'talking blues.'"
Again like "Too Much Monkey Business," "Subterranean Homesick Blues" is in, well, the blues. "The blues," in its most common form the "12-bar blues," is one of the staple progressions in American music, particularly early rock and jazz. The basic form of the blues begins on the root chord. In the case of "Subterranean Homesick Blues" that chord is A major. The blues continues on the root (or Roman numeral "I") chord for four measures before switching to the IV chord. In this case it is the D major. D major is played for two measures before coming back to the A major for another two measures. So far we've got eight of the twelve measures filled in. The last four measures are where musicians like to switch things up the most, but the general pattern involves jumping to the V chord (an E major here), descending to the IV chord (the D major), moving back to the A major, and then closing with another jump to the E major. That might sound complicated, but it's easy to play and easy to recognize.
Dylan changes things up a little, in some ways simplifying things, but his song is definitely in the blues. "Subterranean Homesick Blues" is in cut time, which means that there are only two beats per measure (rather than four, as in "common time") so his blues really go over 24 measures. He also switches to the D major later, and does not choose to descend to the D major after playing the E major. Because the basic feeling of the blues exists in the jump from the A major to the D major, and then the jump from A major to the E major, we won't have any problems calling this the blues. That flexibility lends itself well to improvisation and (if a musician is so inclined) to showing off, which is why the blues have been so popular.
Speaking of showmanship, those electric guitar licks in "Subterranean Homesick Blues" that lay in the lower realms of the mix during the verses come straight from (who else?) Chuck Berry. Berry introduced the world to such a thing as the "guitar lick" as we know it today. The twangy, high-pitched sound, with that characteristic string bending over a blues scale, is all Berry. Dylan owes him quite a bit—but then again, so does most every other practitioner of rock n' roll.
Bob Dylan, who has always been fond of alluding to other musicians and artistic people in his music, should probably be seen here as paying homage to Berry, not ripping him off. As marked as the similarities are between Dylan's song and Berry's, Dylan carries Berry's concepts out on a much larger scope, blending Berry's blues with his own sense of political criticism and his familiar folk style harmonica riffs.