A short story... based on a true story, I think... about the plight of Japanese soldiers in Burma, after their governments' official surrender. A lot of them refused to give up fighting... either due to failed communiations, or belief that the news of surrender was a ruse to trick them into laying down their arms. Remember: up until just about the very end, official Japanese "news" and internal communications painted an outrageously rosy picture of how they were faring in the war. Many soldiers were absolutely crestfallen when news of the surrender came. To them it was seemingly out of nowhere.
The story of the harp deals with one infantry unit in particular, fighting up in the "hill country" of Burma. I won't spoil it. There is also a very interesting account of one soldier so affected by the surrender, he faked his own death and became a (Buddhist) monk at a local temple, rather than return to Japan.