I recently posted a video of Jeff Kashiwa demonstrating the Akai EWI4000s wind controller. As part of his demonstration, he plays a movement from one of the Telemann Canonic Sonatas (well, sort of an arrangement of one).
The Canonic Sonatas are duo sonatas, with both musicians playing from the same part. (You can download free sheet music of the Canonic Sonatas from the IMSLP.) The first player begins, and the second player echoes, one measure behind. If you have ever sung “Row, Row, Row Your Boat” as a round, then you already understand how this works.
Jeff Kashiwa plays the Allegro movement from the first Canonic Sonata all by himself, playing the first part on the EWI and using a delay effect to create the second (echo) part. Here’s the video again—it should start playing about a minute and a half in, and the Telemann goes until about 2:40.
After the 2:40 mark, Mr. Kashiwa uses more sophisticated looping techniques, using some kind of external device. But you can perform the Telemann duet without any extra hardware, using only the EWI4000s’s onboard synthesizer.