The open and close voice commands are used to examine chords whose notes are spread wide on the keyboard.  For example this Cm chord has 2 G notes:

Clicking on the close voice button produces:

The open and close voice commands only works on

chords whose notes are

spread apart.  If a chord is

tightly grouped to begin with,

such as a chord created in

chords mode, the commands have no effect.

And clicking on the open voice button produces:

the redundant G note is eliminated.

When preferences are set to "apply to chord in table", the voice buttons have a red dot on their face.