Wikipedia
The qinqin (秦琴; pinyin: qínqín; Vietnamese: Dan-tru) is a plucked Chinese lute. It was originally manufactured with a wooden body, a slender fretted neck, and three strings. Its body can be round, hexagonal (with rounded sides), or octagonal. Often, only two strings were used, as in certain regional silk-and-bamboo ensembles. In its hexagonal form (with rounded sides), it is also referred to as meihuaqin (梅花琴, literally " plum blossom instrument").
The qinqin is particularly popular in southern China: in Guangdong, Hong Kong and Macau. A similar instrument, the two-stringed đàn sến, has been adapted from the qinqin for use in the traditional music of southern Vietnam.
The frets on all Chinese lutes are high so that the fingers never touch the actual body—distinctively different from western fretted instruments. This allows for a greater control over timbre and intonation than their western counterparts, but makes chordal playing more difficult.
There are two varieties of qinqins in modern China: the "traditional" version, characterized having "tall" Chinese style frets (see photo), and the "modern" version, which uses fret wire instead. The modern version also closely resembles a banjo in that its body shape is usually round and includes a drum head made most often of sheep skin or python skin. The modern version also usually comes with three strings, the tuning of which most people (even the store staff and management) are "not clear" on. I've been told by one salesman who said the third and the first strings of the qinqin are tuned like the two strings of an erhu (inside string = D4, outside string A4), which is a 5th apart, leaving not much room in the middle for the second string of the qinqin. A Westerner would usually attempt to tune it "D-A-d" (D4-A4-D5), but this will usually break the thin string #1. At a second store, the sales lady came and tuned the qinqin I was handling to "G-D-g" (G3-D4-G4) and while I'm not sure if this is the traditional tuning, it seems pretty acceptable. A third source, frequently cited on the Chinese websites, says the tuning is G3-D4-A5. But with the Romance brand instrument I own, and using Alice brand qinqin strings, I always pop (break) string 1 as soon as I get to G4# (a semitone below A5). So, until I'm informed of a better tuning by an authoritative source, I'm sticking with "G-D-g".
For Westerners, the unusual fret spacing and the corresponding notes used in the scale sound "off" or "bad" because they generally do not correspond to the notes of the 12TET (12-tone equal temperament) system used on Western instruments like the guitar and the banjo. Many of the notes appear to be off (either sharp or flat) by about a quarter tone (half a semitone). Because of this, many Western buyers of the qinqin feel disappointed in the instrument after buying them because the notes produced are not the ones expected. However, the human ear can be re-educated and street performers who play this instrument can produce very nice folk music with the instrument. So, unlike the pipa (and some other Chinese instruments), the fret boards of most models of qinqins have not been modernized to support the 12TET standard.
I have also come across a more traditionally designed qinqin built in Shanghai that, from its picture, looks like the fret layout corresponds to the Western 12TET standard and it has 12 frets per octave just like a guitar. A photo appears in one of the external links below. If the future fret layout of qinqins were left to me, I'd fret it just like a mountain dulcimer or stick dulcimer, using the seven Mixolydian mode notes (fret positions) per octave plus fret 6.5 which allows Ionian mode (major scale) songs to also be played without having to re-tune the instrument. I feel the qinqin, with its banjo like sound box would make a great stick dulcimer if only they could work out the fret arrangement.
The approximate bridge position of the "floating" (movable) bridge on the qinqin can be easily calculated by doubling the distance between the nut and the 7th fret. The 7th fret on the qinqin is an octave higher than open string. Since the distance between the nut and the 7th fret is about 11 inches, the bridge should be located about 22 inches from the nut. This means the bridge will be located about 60% across the drum head, or 40% before the tail end of the drum head. For more precise location, take a digital tuner and compare the notes produced on each string, first open string, and then stopped at the 7th fret. The bridge position should be slightly adjusted so the note produced is "spot on" (but an octave different) at both open string and stopped at fret 7. Doing this for all three strings will usually result in a slight tilt to the bridge with the bass string maybe 1 or 2 mm longer than the treble string. This method is often employed with other floating bridge instruments like banjos, stick dulcimers and cigar box guitars. The 22-inch scale length of the qinqin makes it comparable to the tenor banjo.