Today’s artifact of the day came from a really unassuming pile of what looks like a dump of coal, slag, clinker and burnt metal. Nic and Lisa were excavating this context, and discovered a harmonica!
We recovered parts of the comb, two reed plates, and scraps of a leather and oilcloth case.
The comb is the wooden part sandwiched between the reed plates, divided into cells that channel air flow. Most harmonicas now have plastic combs, because wood absorbs moisture from the player’s breath and can expand and affect the playability of the instrument.
The reed plates consist of thin reeds made of strips of metal attached to a rectangular metal plate. Air blown into the comb causes the reeds to vibrate and make the note.
Often the reed plate was nailed to the comb which is the traditional method of attaching them. Other harmonicas have the reed plates screwed in to the comb. Even rarer are cover plates held to the reed plates simply with tension, like some World War II models. Having the reed plates screwed or bolted in means you can replace reed plates when they get worn and start to fall out of tune. In the lab, we’ll be able to determine which is the case with our harmonica.
The last part of the harmonica is the cover plate, which help to direct and project the sound, and also to protect the reeds. While we found parts of the case, we don’t have the cover plates! This is an interesting preservational puzzle. The wood of the comb was (mostly) preserved because the reed plates are made of brass, and the metal salts have acted to preserve the wood. Perhaps the cover plates were a different kind of metal or wood that did not preserve as well as the rest of the artifact.
I took a look at the reed plate, and I believe our harmonica is a tremolo harmonica, using the Weiner system because there are two reeds for each note. Tremolo harmonicas have a unique sound because the two reeds for each note are constructed at slightly different tune, so their waveforms interact against one another and make a warbling sound.
Tremolo harmonicas are very common for playing folk music, and are probably the most common type of harmonica in the world.