Augmented sixth chords as altered dominant chords with flatted second degree Augmented sixth chord

the augmented sixth chord may built on notes other ♭6.

tchaikovsky considered augmented sixth chords being altered dominants. described augmented sixth chords inversions of diminished triad , of dominant , diminished seventh chords second degree chromatically lowered, , accordingly resolving tonic. notes that, theorists insist upon [augmented sixth chord s] resolution not tonic dominant triad, , regard them being erected not on altered 2nd degree, on altered 6th degree in major , on natural 6th degree in minor , yet calls view, fallacious , insisting a, chord of augmented sixth on 6th degree nothing else modulatory degression key of dominant .

augmented sixths dominants in tonality of c, according tchaikovsky. notice resolution of inner voice avoid parallel fifths in last example.




an italian sixth chord built on scale degree ♭2. here italian sixth chord functions substitute dominant, shares third , seventh. schubert s major sonata, d. 959.  play (help·info)

classical harmonic theory notate tritone substitute augmented sixth chord on ♭2. augmented sixth chord can either enharmonic dominant 7th chord without 5th, gr, enharmonically equivalent dominant 7th chord 5th, or fr enharmonically equivalent lydian dominant without 5th, of serve in classical context substitute secondary dominant of v.

original dominant 7th–tonic progression  play (help·info), tritone substitution (♭v/v–i)  play (help·info), augmented sixth chord (it–i)  play (help·info).