Chromatic Air

What model are you playing? Some chromatics are leakier than others.

The one I have is less airtight than I'd like.

You can do a few things to improve airtightness.

1) Remove the covers.

Loosen the reedplate screws, and press the reedplates forward to ensure they're snug up against the mouthpiece assembly.

Re-tighten, starting in the middle of the left-to-right continuum and working outward. Tighten only untl the screwdriver resists your fingers.

2) Unscrew the mouthpiece/slide assembly.

Make sure not to lose the bumper, the little plastic tubes that go around the screws to keep the slide from clanking against the screws.

The four layers are:
--Mouthpiece
--Slide cage (aka U-channel due to its shape)
--Slide
--Backing plate.

You can increase the airtightness of this assembly in a few different ways.

First is to get some rubber cement and use it to coat the underside of the backing plate - the side that goes against the body of the harmonica. This seals air leaks between the backing plate and the harmonica. I learned this from Brendan Power.

The next is to tape the slide. I've never done this but some chromatic players swear by it. You apply Scotch Magic tape to one side of the slide. then cut out all the holes (fussy work!) This effectively makes the slide thicker so that less air leaks through the spaces between the slide, the backing plate, and the U-channel.

You can also reduce the clearance around the slide by shaving down the sides of the U-Channel, but this has to be done accurately and can cause permanent damage if done badly.

When you re-install the slide assembly, place the slide so that the open holes in the slide are on the top row of holes, and engage the slide with its spring.

Place the U-channel over the slide, and make sure that the tabs in the U-channel lock into the notches in the backing plate.

Make sure that the mouthpiece is the right way around, so that the groove in the back of the left end of the mouthpiece is ver the left side of the harmonica to allow for movement of the slide spring poking out through the side.

When you re-tighten the mouthpiece screws, at first tighten them to a general snugness.

Now check the profile of the assembly to make sure that the U-Channel is in parallel alignment with the backing plate and slide. If it isn't, you may need to re-seat it.

Once the parts are in alignment, hold the slide button in and tighten the left-end screw until the slide won't move. Then loosen carefully until the slide springs out. Then do the same with the right-end screw. you're looking for the tightest fit that will still allow easy slide movement.