0
Many harmonica players tend to think of the comb as the “body” of the harmonica – a passive part of the structure that has little real impact on the sound and performance of the instrument.
The reality is quite different. The comb is the part of the harmonica that determines how well or poorly air reaches the reeds, and the material it is made of affects everything from the lifespan of the instrument to the cleanliness with which you can bend notes on it.
What the comb actually does
The comb is essentially the middle part of the harp that divides the two reed plates. When you play a note, you’re directing air through the comb’s chambers into a specific reed on a specific plate. If you ever take the whole thing apart, you’ll notice that without the comb, the reeds just flap around. But without the reeds, the comb can’t do anything. It’s just the reeds that actually make the sound.
Why plastic became the standard
ABS plastic has a moisture absorption rate of less than 0.05%, so it’s effectively impervious to things like humidity, saliva, and temperature. It doesn’t warp. The reed plates can seal against it perfectly each time you play, and then keep sealing, no matter how many times you do that.
Warping is particularly important when it comes to airtightness. If you want a nice, clean bend to a note, air shouldn’t be escaping from anywhere else except through the gap in the reed. When the comb warps out of shape and the seal is broken in teeny, micro ways all over the place… you get the idea. The note bending gets sloppier and requires more air.
Plastic is simpler to clean, doesn’t host colonies of bacteria, and doesn’t need to be stored in a particular way to avoid temperature, humidity, etc.
For those looking for top-notch construction on either side of the wood vs plastic divide, Harmo makes diatonics with CNC milled combs in sealed wood and ABS plastic.
The problem with traditional wood
Pearwood was the industry standard for decades, and the fact is many of the greatest harps ever made were constructed with it. But wood absorbs moisture. And when you’re playing, your saliva and warm breath are being introduced into the comb, causing the wood to swell. This results in 2 immediate, performance-threatening problems.
The flat faces distort, breaking the hermetic seal between the comb and reed plates – and air leaks ruin all your expressiveness. Second, the edge of the comb slots can swell outward, creating a razor-sharp, knife-like edge that you will realize makes playing an absolute torture over an extended period. Unsealed wood can absorb up to 20% of its weight in moisture.
Measurable dimensional change has been observed in side-by-side laboratory comparisons of impregnated and unimpregnated pearwood combs.
The acid levels in saliva contribute to the breakdown of the organic components with each subsequent swell/shrink cycle. So even if swelling isn’t a problem for the first 6 months, the lifespan of a wood comb is less than that of a plastic one.
Sealed wood: a middle path
Modern manufacturers are not complete traitors to wood – they just handle it more carefully. Sealed wood combs such as those treated with lacquer or oil to minimize moisture absorption perform more or less equivalently to plastic. Some manufacturers use bamboo composites, which are naturally denser and less porous than traditional pearwood.
The sealed wood case isn’t acoustic; it’s tactile and aesthetic. Wood feels slightly softer against the lips than hard plastic, and many players prefer that sensation, especially when the harmonica is being played for long periods. There’s also a warmth to the look of a wood-combed harmonica that appeals to players who care about the traditional instrument character.
If you go that way, plan to put the work in the maintenance. Sealed wood is still degraded unless the comb is properly dried out after bouts. It’s a rewarding material to work with.
Choosing the right material for your situation
The choice is easier than it seems once you eliminate the voodoo that’s grown up around wood supposedly having a “warmer” tone.
Beginner? Plastic. You don’t want to worry about maintenance until you’ve had time to develop good playing/cleaning habits. ABS combs play readily out of the box, don’t change, and don’t get sharp if you leave them wet.
Serious player in a humid environment who has to play new sets frequently? Plastic. The consistency matters more than anything else when you’re under pressure to perform.
Sealed wood makes sense if you’re an experienced player who already has good maintenance habits, prefers the lip texture of organic materials, and values the traditional aesthetic. You’re not getting acoustic magic – you’re making a deliberate trade of convenience for feel.
The real driver of tone
The tone produced by a harmonica is largely determined by the quality of the reeds, the tolerance of the gap between the reed and the reed plate, and the airtightness of the assembly as a whole, with the comb being responsible for the latter aspect.
A really good plastic comb will outperform a warped and leaking wood comb every time, no matter how romantic the idea of playing wood may be to you. Choose the material that holds up under your actual playing conditions, not the one that sounds better in a forum debate.