here is Cohon's history of Havah Nagilah:
The man largely responsible for the song's existence in its present form is Abraham Zevi Idelsohn, and he was the father of Jewish Musicology.
As a young cantor, he left his native Latvia, worked in Germany and South Africa, then went to Jerusalem early in this century to pursue his dream of collecting the oral traditions of his people and making them available to the world of music.
In the course of his research he visited a group of Sadigura Hasidim there, in 1915, and wrote down some of their Nigunim. This was one of them. It was a wordless "bim-bom" melody, a mystic chant.
Then came World War I. Idelsohn became a bandmaster in the Turkish Army.
Three years later he was back in Jerusalem again, leading a chorus in a victory concert. The Turks were out, the British were in, there was a Balfour Declaration, and the yishuv (Jewish community) was celebrating. He needed a good crowd-pleasing number to end his concert, and he didn't have one. But he had a file. So he browsed, and as luck would have it his hand fell on this Sadigura Nigun.
He arranged it in four parts, put some simple Hebrew lyrics to it, and performed it. The rest, as you know, is history, as this became the best-known Jewish song in the world.