That code is pretty advanced, they're doing all kinds of fancy stuff with sample play back. The http://danceswithferrets.org/ blog post I sent you has a much better introduction to how to code for the chip.
I am trying to get this code to work, without success. only a drone sound. i have changed my code to match pins after pin 3, which i used for the clock output.
http://milkcrate.com.au/_other/downloads/teensy/SN76489_USB_MIDI_100/SN76489_USB_MIDI_100.ino
i used the teensy clock, not sure where this code should go in the program
Code:
analogWriteFrequency(kPin_CLK, 4000000);
analogWrite(kPin_CLK, 128);