The brackets usually mean it is a ghost note. That means it is played very softly or quickly like it isn't really there. It can also mean it is an optional note that can be played or not. It can also mean that the note has a harmonic overtone. It can also mean this note was hit accidently by the player if the tab is from a note for note tab book. It depends on the context, You need to hear the tune to figure out which it is. Google for ghost notes and you should come up with some examples and more detailed definitions.
Hope that helps.
|