文献称此法自唐代雷氏始。《苏东坡笔记》云：“雷琴独有余韵，应指反复噫喑不已。蜀僧有省涓者，欲求其所以然而不可得，乃破其所藏雷琴求之，声出于两池之间。当两池处其背微隆，仅若韭叶然，声欲出而隘，裴徊不去，乃有余韵。此最不传之妙”。这是对纳音的最早论述。顾恺之斫琴图之中上方槽腹图中，所见二条深色隆起，似为纳音形制。至于纳音的设置是否自晋代已有，仍需进一步研究。
(my attempt translation) Document shows Nayin started from Tang dynasty Lei family... at the area on the top board facing two sound holes, the wood slightly swell, as leek leaves. Sound wants to come out but confined a little bit, lingering around, therefore creates more subtle sound.
although some qin's Nayin is curved in instead of curved out. This picture is my sketch of one of my qin made by Wang Peng.
传世的古琴纳音高低颇不一致。有的古琴，由于几百年间的磨损，纳音多隐而不显。（《苏东坡笔记》所称可能就是属于这种情况，不然纳音从池、沼中即可看到，不必非破琴不可。）但有的琴纳音高，如卫仲乐先生所藏仲尼式琴纳音隆起很高，距底仅有五分。这种高纳音适于面板较薄的琴。笔者所藏“太古遗音”小膝琴，下池纳音系用灰漆作出。修琴时因音浊而剔去，结果琴声混响，散漫不收；后用旧桐木补作纳音，音复清越。可见，纳音并不单是与余韵有关。另外，有的古琴无纳音，但面板很厚而边薄，实际上还是起到了纳音的作用。家姊纪园所弹宋百纳琴，就是这种情况，古琴中亦每见之，不能视为常规。
From handed down ancient qins, one can see their Nayin has different heights. Since several hundred years of wear and tear, some has the Nayin implicit rather than explicit... but some qins has high nayin, swell pretty high, only 5 fen (about 1.5cm) to the bottom. This kind of high nayin is suitable for qin with thinner top board.... some qin has no nayin, but has very thick top board and thin edges, which actually is doing the same function as nayin...
This is interesting Nayin. It could fits the "隐而不显"implicit rather than explicit "面板很厚而边薄" category that the top board is thicker in the center and thinner towards to the sides.
中文資料來源 Chinese Article Source:
http://info.guqu.net/guqinzhishi/20090726164448_26130_2.html
