The front of me is the source of a song
Or to kiss with a fervor of love lifelong.
My back is a plant fit for a queen,
Crafted by needle, chemical, or machine.
Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I’m double, I’m single,
I’m black blue and gray,
I’m read from both ends,
And the same either way.
I may seem real yet I am not,
Once you're gone I'm often forgot.
Time here stretches and it shrinks,
It all depends on how you think.
I may be good, I may be bad,
I may be the same as one you've had.
What am I?