Tracy Chapman: Behind the Wall
I thought a good follow up to Suzanne Vega's "Luka" would be to post Tracy Chapman's "Behind the Wall". I wasn't able to find any internet confirmation, but I was always told that this song was Tracy's response to "Luka". The song is a haunting a cappella song from the perspective of Luka's neighbor, to whom Luka is speaking in Vega's song.
Like in the song, in reality, many outsiders feel helpless to do anything when confronted with domestic abuse around them. We are either silenced by social rules that tell us to stay out of other people's affairs, or we reach out only to find our attempts fail because the powers that be are unwilling or unable to step in.