It seems that the default baud rate for the Vmusic is 9600, leaving us Picaxe8 users out, but looking through the Vinculum manual (USB030.pdf) it states that the baud rate can be changed. Can the picaxe do this and how?
Without having checked, it should be possible to do that from a PC. You'll probably need some sort of buffer to convert voltages and maybe invert the signals, a MAX232 or a simple logic gate. SPI could perhaps even be used via a line printer port.