Here's a nightcap for you:

These are Lissajous figures. The construction of each graph depends on frequency and amplitude (the points of the left and top circles).

Metallica's song "Unforgiven" is a power ballad about the struggle of an individual against those who want to control them. The lyrics of the song tell the story of a young boy who is raised to conform to the world around him, and how he eventually becomes bitter and tired from trying to please everyone. The song's title refers to how the young man labels society as "unforgiven" after his experiences. 

… New blood joins this Earth
And quickly he's subdued
Through constant pained disgrace
The young boy learns their rules
… With time the child draws in
This whipping boy done wrong
Deprived of all his thoughts
The young man struggles on and on, he's known
… Ooh, a vow unto his own
That never from this day
His will they'll take away
… What I've felt, what I've known
Never shined through in what I've shown
Never be, never see
Won't see what might have been
… What I've felt, what I've known
Never shined through in what I've shown
Never free, never me
So I dub thee unforgiven
… They dedicate their lives
To running all of his
He tries to please them all
This bitter man he is
… Throughout his life the same
He's battled constantly
This fight he cannot win
A tired man they see no longer cares
… The old man then prepares
To die regretfully
That old man here is me
… What I've felt, what I've known
Never shined through in what I've shown
Never be, never see
Won't see what might have been
… What I've felt, what I've known
Never shined through in what I've shown
Never free, never me
So I dub thee unforgiven
… What I've felt, what I've known
Never shined through in what I've shown
Never be, never see
Won't see what might have been
… What I've felt, what I've known
Never shined through in what I've shown
Never free, never me
So I dub thee unforgiven
Oh-ooh-oh
… Never free, never me
So I dub thee unforgiven
You labeled me, I'll label you
So I dub thee unforgiven
… Never free, never me
So I dub thee unforgiven
You labeled me, I'll label you
So I dub thee unforgiven
… Never free, never me
So I dub thee unforgiven