The Jewish National Library in Jerusalem has worked the miracle of digitizing, among other works, the 10-volumes of the Abraham Zvi Idelssohn Thesaurus of Oriental Hebrew Melodies, first published in 1923. Idelssohn, known as the father of Jewish musicology, participated nearly a century ago in field recording work in then Palestine. He recorded Jews and and non-Jewish residents of the area, taking meticulous notes both of speech, education and background of the informants, and transcribing into notation their songs from the wax cylinders her made there. From his field work and other research, he produced a ten-volume monumental study which became the basis of musicology of the various Jewish musics from throughout the world, both sacred and secular. Now, this marvelous resource of Jewish music is available online from the JNUL website.
http://www.jnul.huji.ac.il/dl/books/html/bk_all.htm