The Sound Archives include recordings of sections of prayers and religious poetry, devotional song, ceremonies, folksongs and artistic music totaling tens of thousands of hours of recordings. The materials were produced by researchers and musicians from the early twentieth century onward. Indeed, the recording work continues to this day, in order to document the evolving musical traditions of all communities in Israel, with a preference for primary sources wherever possible. This work is undertaken during events around Israel, as well as through meetings in interviewees’ homes and sessions in the archives’ recording studio. As part of this work, an enormous effort is made to document the beginnings of modern Hebrew song. Studies and CDs based on the Library's collections (e.g. Nights in Canaan: Early Songs of the Land of Israel (1881-1946), edited by Yaacov Mazor) are published by the Jewish Music Research Center of the Hebrew University of Jerusalem that is also located at the National Library.  The archives of researchers and collectors include lists and summaries, drafts, prints, field recordings, photographs, and so forth accumulated during the course of their musicological work. Key archives include those of the Jewish music collectors Yaacov Michael and Meir Noy. In addition to Noy’s collection of Hebrew songs, he also collected Yiddish songs, which are one of the main sources of Hebrew song and are uniquely represented in Israel. The archives also include materials used by performers, including cantors’ notebooks, scores of Hassidic songs and Ladino songs written down during meetings with informants.