There may just be an order to powering on. Maybe the Uno needs to be running before the Yammie is powered on, or the reverse. Could be a quirk in the keyboard where it either needs to see the Uno at startup, or it needs to boot first and then be connected ...

or it could be the Uno that needs to be connected to a live device, and not boot up to a dead connection (which possibly causes it to stall)

just guessin' at this point


Make your sound your own!
.. I do not work here, but the benefits are still awesome