The term action means a different thing for a harmonica than it does for stringed instruments like the guitar, though the basic premise is the same. It’s a term that refers to how easily the reeds respond to changes in air pressure. You can adjust the action on a harmonica by bending the reeds or adding shims to give them more distance from the reed plates. The Harmonica for Dummies blog has a great post on how to do this that you can read at.

Materials

The materials used in the construction of the harmonica are what will determine the specifics of the instrument’s tone. Aside from considerations like overall build quality, it’s the most important thing you’ll need to consider once you’ve decided what size of instrument you’re looking for.

There are three major areas of the harmonica, which will often each be made from a different material:

The comb (or body) The reeds and reed plates The cover

All three of these areas will have an impact on the sound, but the material in the comb and reeds is especially important since it will also affect the instrument’s playability. As a result, these are also the areas where you’ll see the most variation.

Let’s start with the easiest section first: the cover. These are the outer plates that enclose the instrument, both to protect the interior components from damage and to add resonance to the tone. They’re usually made of metal, with stainless steel and chrome being popular choices. In the extreme high end of the harmonica world, you’ll find covers made of silver and other expensive metals that can greatly alter the instrument’s sound. The materials used in the under $1,000 category have less of an impact on tone.

The comb or body of the harmonica is what makes up the bulk of the instrument. It’s the rectangular portion between the cover plates. It holds the reeds and contains the holes you blow into to produce sounds. Unlike with covers, you’ll find a huge variety of materials being used to make the comb—and an equally wide array of opinions about which material is best.

Traditionally, the comb was made from wood. You will sometimes still see wood utilized in modern harmonicas, but it’s more common to see combs made of either metal or plastic. The polymer ABS (acrylonitrile butadiene styrene, for the science folks out there) is a popular choice because of its durability. You’ll also find a lot of different metals used, from inexpensive minerals like aluminum to rarer metals like titanium in high-end models.

There’s some debate in the professional community about how much impact the comb material has on the sound, but there’s no question it’s one of the main factors in the instrument’s longevity and playability. While traditionalists prefer wood combs, most modern players would rather use plastic or metal. Wood tends to warp from humidity, making it harder to play over time. Metal and plastic are also easier to make air-tight, very important for an even response across the instrument.

The sound of a harmonica is produced through vibrations of the reeds, which are flat pieces of metal secured at one end. The free end responds to your air, blocking and unblocking the various holes and making the sound. It’s universally agreed the material used in the reeds has a big impact on the harmonica’s tone, and are arguably the most important single aspect of the instrument to consider.

Brass is the most common reed material, but other metals are often used. Stainless steel is one popular option, as is silver, and you may see techniques like chrome plating employed, too. In general, the heavier and harder the metal, the darker and warmer the resulting sound will be. Harder metals are also more durable, meaning your reeds will last longer before you have to change them.