Sullivan wrote “Ivanhoe," so to speak, with  his life-blood. He slaved at it steadily from May till December, and put into it only of his best.  For weeks before he finished it he was inaccessible; the Christmas of 1890 was no holiday for  him. The rehearsals had begun long before the  orchestration was ready, and the opera was to  be produced on January 31, 1891, at the latest.  By the first week in the new year the score was  completed. Then Sir Arthur told me I might come to Queen's Mansions to hear some of the music.  To my great delight, he played several of the numbers for me. I found them picturesque, dramatic, original, and stamped throughout with the  cachet which the world understands by the word “Sullivanesque”. I was particularly struck by the Oriental character of the harmonies and “intervals” in Rebecca's song, “Lord of our chosen race," and I told Sullivan that I thought nothing could be more distinctively Eastern or even Hebraic in type.   

“That may well be so," he rejoined. “The phrase on the words 'guard me' you especially refer to is not strictly mine. Let me tell you where  I heard it. Wlien I was the 'Mendelssohn scholar' and living at Leipsic, I went once or twice to the  old Jewish synagogue, and among the many Eastern melodies chanted by the minister, this quaint progression in the minor occurred so frequently  that I have never forgotten it”. It certainly comes in appropriately here.