The Jewish National and University Library of Hebrew University on Givat Ram contain the National Sound Archives and several large special collections of Jewish music. Among these are the A.Z. Idelsohn Archives, the recordings collection of Robert Lachmann and recordings of music from Jews around the world. JNUL contains an excellent thesaurus of articles about Jewish music and works closely with the Department of Musicology of Hebrew University and the Jewish Music Research Centre. At some point in the near future, the Jewish National Library and Sound Archive will move to a new facility.
http://jnul.huji.ac.il/eng/