Yamaha provided a large no. of scat type voices, and for me most of them are to be avoided apart from curiosity. Being very selective can help, trying to avoid those that are very repetitive and especially those that promote the "annoyingly intrusive sibilance of Shoo"
If you get the right mix of voices they can be very responsive,
and can be addictive to play in the privacy of your own home, although not maybe to push your luck in a public performance!

Here's an mp3 of some doodles using an ensemble of different voices in R1,2,3 and the Left voice. There's no multi recording/overdubbing involved.

http://www.box.com/s/4c5466yv3gg6fr22v97n


John