Italian 6th chord
a.) in first inversion
b.) flat 6 - 1 - #4
c.) double the tonic
d.) resolves to a 1 6/4 chord

German 6th chord
a.) flat 6 - 1 - 3 - #4
b.) resolve to a 1 6/4 or a V chord


French 6th chord
a.) flat 6 - 1 - 2 - #4


What are special about these chords ?

Why does classical composers use these chords?

How are there chords used ?