Not a mandolin, but finish question

So the latest thrift store buy is a Chinese moon guitar, a yuekin I think. Aside from the fun making bamboo frets half an inch high (!) as some are missing and wondering about the totally invisible insides, it appears that the top and back are unfinished.
Does anyone know if this is usual? I’m tempted to mop a little shellac on just to keep it clean.
The sound hole is something the size of a fingernail, and totally hidden under the bridge, which is interesting. There’s also a plugged hole at the back of unknown function. Attachment 189780

Info here on wikipedia. Proper spelling in English is yueqin.

The most interesting fact is this under the Traditional Yueqin section:

Quote:

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There is no sound-hole, but inside the sound box are one or more strands of wire attached only at one end, so that they vibrate, giving the instrument a particular timbre and resonance.

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I don't know of the modern version has that or not. I assume yours is a modern one. I have no clue as to whether it was supposed to have finish on the top. I would guess that, like some old Italian bowlbacks, that there might be a very light oil finish that disappears with age.

I have been obsessing over a liuqin and started a thread under that title. It is a small pear shaped instrument similar in size, shape and tonal range to a mandolin. It also has those raised bamboo frets, sort of like small bridges. I think the modern ones and ones that the better layers play have metal frets embedded into the top of these wooden ones.

Yes, that’s why the invisible interior is interesting. Supposed to act like the springs under a snare drum. Maybe they’re attached to that plug at the tail end, but it might not be advisable to mess with it. This one almost certainly modern, at a guess low-end quality although the pegs are a bit fancy. Have to do a bit of carving on one as the decorative finial is missing. That, and missing frets points to glue issues, so maybe traditional stuff. Also the fret spacing needs research, as expected. I

Check the Liuqin thread. There a few knowledgeable people there. The consensus was that the original scale on the old instruments was different from our Western scale but the modern instruments are intonated the same as our instruments. The standard BTW for many of these modern Chinese instruments seems to be what we fiddlers call cross tuning: GDGD or DADA. So they could easily be tuned to mandolin or mandola tuning.

Interesting. I wonder if the ruan instruments have that same internal contraption.

I actually found a xiaoruan (similar to your yueqin) used at a US music store. I just received it last week and, yes, the top and back are made of paulownia wood and is unfinished as far as I can tell. My xiaoruan is the equivalent of the mandola in the ruan orchestra family. The scale on mine is 18" and the standard tuning is DADA (low to high). I am thinking of trying heavier strings and tuning it to octave mandolin tuning.

Attachment 189974

Yes, paulownia seems to be used on these. An otherwise uninformative you tube video I found that involved opening a yueqin showed a banjo-like stick in the drum from the neck to the tail, which explains the plug at the latter point. The floppy spring rod was attached at the rim on a (single) cross brace forward of the bridge, but I’m not certain. Similar construction possible on yours, except that you have a tailpiece. My yueqin is definitely set up for three strings according to the bridge, but has a fourth peg hole now occupied by a hanging cord. Necessity involves ignoring hobbies for a while, so this project shelved.