Secondary Functions: replace the primary functions Tertiary chords: take on the function of those around them by extending/embellishing; they work in chromatic and diatonic harmony
If you see a I6/4, it is most likely functioning as something other than the tonic.
There are four types of second inversion chords:
Second inversion triads have to be tertiary function.
Doubling rules:
Cadential 6/4 chords
Label it using a bracket to show dominant function:
I6/4 V I |____| V D ———– T
Passing 6/4 chords
I - V - (ii6/4) - V6 - I pass T D————— T
Pedal 6/4 chords
The pedal does NOT have to be in the bass, but it is almost always in the bass
I (IV6/4) I ped T——————