How can more than one sound be played at a time from the Supernova II?

You need to use the Supernova II in it's Performance mode. Programs can then be assigned to any of the 8 parts of a Performance. Download the help pdf "a guide to using the Supernova II Multitimbrally with a sequencer" above for full detailed instructions.

http://www.novationmusic.com/support.asp?supportid=16&view=TandT