Now I know that this seems like I'm taking the easy way out by choosing xylophone for my 'X' post but I am actually going to tell you something that may or may not prove useful in the future.
I have known for sometime that the main difference between a xylophone and a Glockenspiel was that one was made of wood and the other was made of metal. But I could never remember which was which.
So I devised a way for me to remember this fairly useless fact (unless you are a xylophone or Glockenspiel player), which I will now share with you.
A Glockenspiel is made of metal and a xylophone is made of wood.
And the way that I remember this is...
A xylophone begins with X.
X is the letter straight after W.
W is the first letter of the word wood.