Jill, interestingly enough, I recorded live about 4 years ago, the Andrew Sister's hit: "Boogie Woogie Bugle Boy" utilizing the built in vocalizer in my arranger keyboard (Technics KN5000) of that time. Re-listening to my recording now, I admit there've been a lot of improvments made in harmonizer sound quality and recording skills since then, but my rendition does include 'vocal harmony throughout'. I invite you to visit my website and listen to my afore-mentioned song, as well as other songs & video clips:
http://scottyee.com
Click on: 'Song Demos' Page link

My "Boogie Woogie Bugle Boy" demo is located in the Big Band/Swing Section.

Jill, looking forward to hearing your rendition (including vocal harmony) of Bie Mir Bist Du Schoen. I'm sure you'll sound a lot more like the Andrew Sisters than I did.

Scott