From restoration investigations reports of the Shosoin Repository and from the existing collection of instruments in the Shosoin Treasure house of Todaiji Temple, experts know a great deal about the musical system of the time.
Nara period’s most important musical instruments used in the music of Tang dynasty China are preserved in the Shosoin Treasure house (8th century and therefore the world’s oldest musuem). Many of these have been kept in complete form; others have been restored. Copies have been made for various museums for viewing.

Five stringed biwa musical instrument, design of camel rider in mother-of-pearl inlay. Copied from the 8th century original of Nara period (Exhibit at the Tokyo National Museum)
The instruments played in the Nara period found in the Shosoin include:
1) kin (chin in Chinese) seven stringed zither
2) biwa (pipa) four stringed lute
3) genkan (juan-hsien) four stringed guitar
4) shakuhachi (chipa) flute
5) oteki (heng-ti) flute

Shakuhachi, Shosoin Repository (Imperial House Agency)
6) sho (sheng) mouth-organ
7) u (yu) large mouth-organ
8 ) gogen-biwa (wu-hsien pipa)
9) so (cheng) thirteen-stringed zither
10) shitsu (se) 24 stringed zither
11) kugo (kung-hou) harp

Harp (Reproduction ) , Meiji period, 19th century, Original: Nara period, 8th century (Tokyo National Museum)
12) sho (hsiao) panpipe
13) hokyo (fang-hsiang) metallophone

Lacquered drums, Shosoin Repository (Imperial House Agency)
The instruments were played at court and at temple ceremonies and their use was described in the Dedicating Record of Todaij.
Can you help in refering me to Japanese traditional musical instrument stores where I can buy a Biwa?
Thank you
This page lists a few stores, try Nichiwa’s Musical Instruments : http://www.jp-stores.com/en/c2_en.cgi?c1=11&c2=Japanese-instruments / or else online: http://www.worthpoint.com/worthopedia/old-japanese-biwa-lute-musical-instrument-needs
please post all the most important instrument in one country
help im trying to find is all the pipa house in shosoin are from Tang dynasty emperor given to the japanese emperor?
which would make sense, as anything from tang court is precious in 8th century, while everything u made urself would have been used instead just treasured