Why is that? Is the higher voltage drop of a led, compared to other types of diodes, required?
From what I understand, you can't, in most applications, because both musical keyboards and typing keyboards need to be able to deal with multiple keys pressed at once. With Charlieplexed key matrices, you can't avoid "phantom" key presses appearing when multiple keys are pressed. So only applications where it would be the case that only one key is ever pressed at once would Charlieplexing be used. Am I right?