Bisonoric

His instrument also could sound two different chords with the same key; one for each bellows direction (a bisonoric action).

They are generally bisonoric, use a different style of "long plate" reeds, and tend to be square rather than hexagonal. citation Unlike the English and Anglo, they sometimes have more than one reed per note, creating a vibrato effect.

While the right hand is bisonoric, the left hand follows the Stradella system.