As I was eating lunch today, I heard on a Live365 station, 'Istanbul' dueted by Bing and Ella, with the trumpet riff by Ziggy Elman. This version is apparently from a Crosby radio broadcast; I'm not sure if he/they recorded it for separate phono sales. The performance is available on some CD compilations of Bing's radio music. But, honestly, the Four Lads version is much better.