You’ve pasted together lines from different sources without making sure that variable names are adapted.
Processing is case-sensitive, so it interprets chord_Bank2 and CHORD_BANK2 as two separate things.
First, you’re creating chord_Bank2 but never filling it. But you’re trying to access its contents and that will lead to an error (indexOutOfBounds or nullPointer).
You’re also creating and filling CHORD_BANK2 but then are never accessing any of its contents.
Pick one variable name and run with it.