Can you help me find out the background of the koto song "Nanniwan"?

"Nanniwan" is a guzheng piece based on the song of the same name composed by the famous musician Mr. Ma Ke in Yan'an in 1943. The music absorbs the tones and rhythms of folk songs and dances, and is beautifully lyrical and danceable. The music is full of joyful emotions from the beginning to the end, and is a hymn to the heroes. The structure of this piece is short and simple, with a few lines outlining the warm scene of the army and the people on the land of northern Shaanxi, singing and dancing together. After adapting the piece to zheng, there are two special finger-carrying methods that deserve our attention: first, the strong beat is handled by the middle finger's "hook" technique, which adjusts the relationship between the finger order's "smoothness" and "reversal". For example, the alternate use of "hook to hook" on the strong beat of the second line, measure l, avoids the repetition of fingers and transforms "reverse" into "smooth". Secondly, the skillful combination of "hook" and "even support" not only sounds novel in the sound, but also the alternation of high and low tones constitutes a simple two-part singing effect, which is a novelty. For example, the third line of the third, fourth, fifth and sixth bars, is such a finger order arrangement. Single finger continuous finger, unless it is scraping, generally in the rhythm is very difficult to grasp, because the alternating fingers in the normal rhythm suddenly turned into a single finger continuous finger, it is easy to cause an imbalance in the center of gravity, just like our feet in the fast running suddenly turned into a single-footed jumping, very easy to fall because of the imbalance. Therefore, we should not treat such techniques as "Lian Tuo" or "Lian Hook" or "Lian Wipe" lightly, and we should pay attention to the way and method while practicing them, not just accurate use of fingers. You should not just use your fingers accurately, but also pay attention to the reasonable use of force. This is especially true when using "continuous hook" and "continuous wipe" alternately. To learn to use inertia and symmetry of the reasonable conversion, finger force and arm force coordination, in order to solve this problem.