Is there any such thing as “Jewish music”? Richard Wagner was pretty sure and wrote a bilious screed on the subject. And a conference in Flanders last week, connected to this production of Fromental Halévy’s 1835 opera The Jewess, explored the idea in the realm of opera.I didn’t go to the conference, though I did see the opera. No doubt there is lots to be said, but also the risk of merely compiling lists: stereotypes in nineteenth-century opera, for example; composers of Jewish origin (many of whom converted with unknown levels of conviction) – Mendelssohn, Meyerbeer, Mahler, Offenbach; biblical texts as subjects for opera and oratorio (though these were usually encrypted metaphors of local issues, like Handel’s works evoking British Israelites