A bit confused at the moment regarding when a perfect fourth is classed as a consonance, and when it is classed as a dissonance. I have read here on Stack Exchange, that perfect fourth intervals are consonant when they are inverted perfect 5ths, unless they involve the bass- (eg 64-53).
Essentially, it is my understanding that:
If a fourth is created by two chord notes in the upper voices, this can be treated as a consonance, and therefore does not need to resolve.
If the fourth is created by two upper voices that are not both chord notes, then this requires resolution.
If the bass is one of the voices, the fourth requires resolution even if both voices are chord notes.
In my example, bar 22 is Dm7 (ii7) in third inversion, followed by G (V) in first inversion in bar 23. The parts concerned are alto and tenor (alto clef). I would like to put a G (anticipation- highlighted) in the alto part. This non chord note forms a dissonance of a second with the F in the tenor part below. In the next bar, the two voices form a 4th, D-G (two chord notes of the GM chord). Is this fourth classed as a consonance, because it is an inverted perfect 5th in the upper voices? Or is it a dissonance, meaning that putting in a second interval before it is problematic?
