I've been learning a little about classical composition and voice leading in classical harmony. I have learnt that in the majority of cases a dissonant 7th should resolve downwards, and the 7th is considered very sricktly.
Any way, i have just been messing around at the piano with the 12 bar blues. The progression i have been using is I b7-I b7-I b7-I b7-IV b7-IV b7-I b7-I b7-V7-IV b7-I b7-I b7. ( where b refers to a flattened 7th)
I have noticed that the progression results in some odd voice leading of the 7ths.
Let me explain: when I b7 progresses to IV b7 the 7th leads occording to classical principals and resolves downwards i.e. the 7th of I b7 falls on to 5th of IV b7, (in classical terms, the correct resolution).
But when IV b7 progresses to I b7, the b7th of IV b7 ought to move to a supertonic, but there is no super tonic in I b7. My 7th of IV b7 ascends a semitone instead, to the 3rd of I b7, the mediant, and therefore doesn't resolve?
Also when I b7 progresses to V7 a similar leading occurs with the 7th of I b7, which ascends a semitone to the 3rd of V7?
When V7 progresses to IV b7 the behaviour of the 7th in V7 is understood; the 7th in this case remains stationary, it transforms and becomes the root of the IV b7 chord. The next chord then contains the sought after resolution, namely the mediant, the 3rd of I b7.
After doing some reading on jazz and blues chords, they mention that some 7ths are so indicative of the blues sound, that they are treated as consonants of the chords; it seemed to indicate only I b7 in the instance, which is why the last chord of my progression doesn't resolve.
Can any one explain to me the odd (new) behaviour of the 7ths in the 12 bar blues.
Are they just considered as consonant 7ths, and therefore have no requirement to resolve.