A harmonica player named Walter approached a Hohner technician at a recent road show. He had a Blues Harp in new condition but the draw reeds made no sound. The technician tried the harmonica and the reeds played smooth, clear and effortless throughout. Puzzled, the tech handed the harmonica back to Walter and asked for a demonstration. Walter wailed away, attacking the reeds with very hard pressure and restricted throat muscles. Under such aggressive technique the reeds could not initiate — they were being choked.

The tech mentioned to Walter that an easier blowing technique would result in a more consistent sound. “I don’t know about technique and stuff,” Walter said, “I just know my harmonica shouldn’t be like this. It should respond to me.”

For the player, response is a term used to describe how quickly and effortlessly a reed sounds when air (breath) has been introduced. If the note sounds clearly and immediately it is “good” response. If the reed makes no sound or a weak sound, it is “bad” response.

Often all that a player should do on an otherwise well set up harmonica is adjust their breath pressure to find the optimum response point for a harmonica. However many players prefer not to adjust their well-practiced and personal technique.

When changing technique is not an option, adjustments to personalize response are made to the harmonica itself.

In terms of harmonica function, response is determined by how well a reed travels through a reed slot when a given amount of air pressure is applied. For good response the entirety of the reed should enter the slot all at once or at least rivet side slightly before the tip. If the tip of the reed is the first to enter the slot, the response will be poor.

Optimizing reed travel to match a player’s personal technique involves adjusting a reed’s gap and curve.

A gap, also called an offset, is the distance between the tip of a reed and the reed slot when the reed is at rest. Every reed needs some gap. If the reed is flush or almost flush with the reed slot, chances are it will not sound at all.

On any particular harmonica, the gap varies from reed to reed. As a general rule, the thickness of any particular reed at the tip determines the proper offset between that reed and the reed plate. Therefore, the lower pitched, thicker reeds need more offset. Gradually, as reeds get thinner and the pitches get higher, the gap diminishes.

For optimum reed response at softer breath pressure you want smaller gaps. Harder pressure means larger gaps.

Before you begin to make your gap adjustments, make sure your reed has a proper curve (see below). Ideally, the rivet end of the reed should be flat and almost flush with the reed plate. From a third of the way from the rivet end and continuing to the tip, the reed should curve slightly upwards and away from the reed slot. This shape is called reed curvature or reed profile. The space between the tip of the reed and the reed slot is the gap.

To adjust the reed gap and curve you need a short, stiff file and your finger or thumb. If you do not have the right type of file, HOHNER offers it as part of a service kit containing tools for gapping and other common repairs. You can order it from the Hohner Parts & Service Center.

First disassemble your harmonica. Remove the reed plates from the comb.

Set your gaps by adjusting the curvature of the reed. Look at the reed from the side. If there is very little or no curve, you need to make one. Place your finger over the rivet third of the reed and press down lightly. Slip the stiff file between the reed and reed plate and gently lift the tip of the reed using short strokes (see illustration).

Do not to overdo it. Make very small changes. Repeat the process as many times as necessary to form a good curve and desired gap. Make very small bends to the reed each time. Pluck the reed occasionally to allow it to settle into its natural shape. More adjustment may be necessary after plucking if the proper curve or gap is not evident when the reed comes to rest.

While you are shaping the reed into the proper curve, be conscious of the size of your gap. Adjustments on both gap and curve should happen simultaneously. At this stage you want your gap staying within the general rules of gapping outlined above.

When you have the gap and curve set, test the response. Place the reed plates on the comb, holding them tightly together – as airtight as you can manage. Blow or draw into the harmonica with the same breath pressure you would use in a real life situation. Consistency is key. A consistently gapped harmonica plays better and is more durable.

If the reed sounds weak or airy the gap is too large. Decrease it by using your finger or a pick to press the area of the reed from the rivet end to the halfway point down toward the reed slot. Make small changes. Do not to apply too much pressure all at once.

If the reed doesn’t sound at all the gap might be too small. Increase the gap and the curvature of the reed by sliding your file between the reed and the reed slot and lifting the reed slightly.

During either adjustment pluck the reed occasionally to determine where the reed will come to rest. Be careful of going too far in either direction. The objective is to find the gap that is just right for you.

In the end, the Hohner technician increased the gaps on Walter’s reeds and Walter was more than satisfied. “I could never play this harmonica and now I can. Thank you Mr. HOHNER man!”