Hey there,
To explain what’s happening under the hood:
The Aeros and the BeatBuddy both respond to most CC:113 command values in the same fashion
CC:113 value 1-6 chooses parts on the Aeros, and CC:113 value 0 starts that transition
On BeatBuddy, CC:113 values 1-32 start the transition loop on the BeatBuddy, and sets the part to which the BeatBuddy will transition to. If the part does not exist, the value is ignored (e.g. CC:113 value 11 is sent but the BeatBuddy song does not have 11 or more parts). CC:113 value 0 stops the loop and finalizes the transition at the next measure. CC:113 value 126 and 127 choose the next or previous part on both units.
When the BeatBuddy Transitions, it sends a CC:102 command by default in order to control the Aeros transitions. In 2x2 mode, the Aeros will switch parts immediately when it receives this command. In 6x6 mode, it will switch to a part if that part is currently selected (and not the currently open part). This can be turned off in the BeatBuddy settings (Main Pedal > MIDI Settings > MIDI Out > Next Part (CC-102))
It may make sense to adjust some settings in other configurations like when using the MIDI Maestro.
The MIDI Maestro CC:113 value 1-6 and 0 commands all work the same on both Aeros and BeatBuddy, as do the CC:113 value 126 and value 127 commands (Previous and Next Part; require CC:113 value 0 sent afterwards in order to work)
You could send any of those commands to both units to control both at the same time and switch parts, just set the CC:113 value 1-6, 126, or 127 command to be sent on the press and send the CC:113 value 0 command on the release, one tap of the button will send both required commands or you can hold down the button to release when you want the transition to occur. In the case the MM is doing all the switching of parts, you may wish to disable the CC:102 command from being sent by the BeatBuddy as it is superfluous.
Check out the full list of MIDI commands here
Watch a tutorial on the MIDI Maestro Custom Modes here
Hope this is helpful, although maybe overwhelming haha!
Thanks for the question