This device is a modification of the Master Pitch device requested by a Reddit user, to have different transposition groups. The device sends MIDI transpose information when it is set to Sender mode, and receives it when it is set to Receiver mode.
Transpose information is sent / received between device that have the same ID. A maximum of 64 IDs can be set, allowing to have 64 different transpose groups.
Every time a device is set to Receive, it receives the transpose information automatically. But when the ID of a device set in Sender is changed, the transpose information is not sent until the controls are changed or the RESEND button is pressed.
This device is free. Consider making a contribution if it is useful for you.