Hey, tell me if it works!

Chromatics can be temperamental beasts. Not only can the slide get sticky, the little valves (those white plasticky bits over the reed slots) can play up like mad. Valves can stick, buzz and pop. In most cases you can avoid such difficulties by thoroughly warming your harmonica before playing it. I use those gel hand-warmers, the ones you boil up to regenerate after each use, to keep my chroms cosy during the session. Just activate one of the hand-warmers and put it in some kind of bag with your harp. Works a treat. If you can ever get a stone-cold chrom to play properly you've had a lot more luck than I ever have!

If you can't track down a hand-warmer, you could always try the time-honoured technique of putting the harp down the front of your trousers for ten minutes or so. Don't demean yourself by putting anything less than a 16-hole harp down there, though, and be prepared for lots or people to think that you're pleased to see them.