The song is a blues song. What defines "blues" is not the popular 8 and 12 bar structures. A lot of barrel-house blues of the kind that Bessie Smith grew famoius on had very complex structures not closely related to 12 bar. There are numerous blues that use minor chord structures. So the musical pattern is not the defining characteristic, it is simply a "majority" characteristic. The chord structure is not modern either -- it is as old as Greensleeves. It is not a chord pattern often used in blues, but so what? It was surely known to the tailgaters who built the bridge to Dixieland music from the blues.

It's a blues song because it wails the blues, man, in an earthy, straight-on sort of wail, like all the best blues do.

A