Brewskio:
Here is some more insight. I am trying to make my own frameless laser harp. My end goal is to have a locked box open or a hidden door open only when the right notes have been played in the right order.So it isn't that I want to do things in a certain order but rather when the notes are played in a preset order then the Arduino sets a pin HIGH.
Then a state machine as described above will work by examining input.
The problem is exactly the same as a password unlock, of which there are a bazillion examples in this forum that you can search for.