How to Clear Obstructions from Your Harp
When a reed on your harmonica won’t play or makes some kind of sound other than a beautiful, clear note, it’s usually obstructed for one of the following simple reasons:
Gunk (such as lint, hair, breakfast remnants, or something else that doesn’t belong) has lodged between the reed and its slot.
Burrs have been created by something hard or sharp nicking the edge of the reed or the slot.
The reed is out of alignment and is hitting the edge of the slot.
Take a look here to clear gunk and burrs from a reed.
If you suspect that gunk or burrs are to blame, figure out which hole number the obstruction is in and whether it’s the blow or draw note. Then remove the covers. If the stuck note is a draw note, look at the reedplate with the reeds on the outside. If it’s a blow note, look at the reedplate with the reeds on the inside.
Starting either from Hole 1 (with the longest reed) or from Hole 10 (with the shortest reed), count over to the hole with the problem. When you’re at the correct hole, follow the directions for the particular obstruction that your harp is afflicted with:
Gunk: Look for lint, hair, or anything else that’s stuck between the reed and the slot and then remove it. Always remove debris by sliding it toward the free tip of the reed. That way you avoid wedging it farther between the reed and the reedplate. By doing this, you also avoid snagging or deforming the reed or yanking it out of alignment.
If the stuck note is a blow note, you may need to shine a light on the reedplate or in through the holes to find the obstruction. Carefully remove any debris you find. You may need to remove the reedplates from the comb to get the obstruction out.
Burrs: Examine the spaces around the reeds by laying a piece of white paper on a table and shining a bright light on it. Remove the reedplate from the comb and hold it so that you’re looking through the reeds to see the light reflected from the paper shining through the reedplate and around the reeds. With this technique, you can see any obstructions, such as burrs.
To clear a burr, slide a piece of steel shim (about 0.002 inches or 0.05 millimeters thick) between the reed and the edge of the slot. You’re trying to sweep out obstructions and slice off anything that sticks out. Be careful not to shift the reed to one side, however; otherwise, you’ll have to shift it back into alignment.