I've been trying to get my VMUSIC2 working with my Arduino, but for the moment to debug other problems I've just got the VMUSIC2 connected to an FTDI serial -> USB.
The problem is, when I first power up the VMUSIC2 and issue a V3A command I get a loud volume, if I then issue "VSV 0" it goes much quieter. If I then issue "VSV 254" it's the same volume. I only get a volume change when doing "VSV 80" (it goes a bit quieter), and then goes up slightly at 0 or 254. I think 254 is ever so slightly quieter than 0, but it's so small a difference I can't tell.
I've had to put the project on hold as I've got a lot on, so I didn't solve the problem.
However what I did do was contact Viniculum (now part of FTDIChip it seems), who said it must be a problem with the audio codec chip and passed me on to them. But I did a little more digging and it seems the VMusic 2 doesn't have number formats very well, since even trying to write the volume registers directly caused problems.
So I think what might work is using the binary UART mode instead of ASCII. Give it a try and let me know how you get on.