Check your Spokes
 

Kicking myself for not doing this before (JMo had problems in the US), most of mine needed nipping up and a couple were noticably loose. They play a nice tune now.

Always do, habits die hard! Whenever I change my tryes I just go around the spokes with a small spanner, tapping them. If they make a dull ring then loose. Usually only takes a turn to get a nice ring. If you need to take too many turns then the spoke just might go into the innertube, through the protective tape! That's not good:Mandy: