is this actually achievable with arduino?
but build 2 midi-inputs
the crucial point is, that i don't want the synth to react to the stroke of the keyboard,
only to the stroke of the drum, obviously using the note-value of the keyboard.
So what do you want the keyboard to trigger?
Are you saying that you want to disregard the note that the drum sends and send a mapped value from the last keyboard note when the drum machine sends anything? If so that is still on with an arduino but I don't see how in practice you will play this.