The DVORAK layout can be seen here: http://www.mwbrooks.com/dvorak/layout.html (http://www.mwbrooks.com/dvorak/layout.html)
Now, the keys "ZXCVBNM,./" are one octave on the virtual keyboard, the keys "ASDFGHJKL;'" another, and the keys "QWERTYUIOP[]" yet another. Looking at the DVORAK layout above, you see where this is a problem?
(Clue for those wishing not to think: I hit Z to play a C note, then I have to hit X, six keys to the left of Z, in order to play the D note above that C, which just doesn't make sense.)
I do have a MIDI keyboard (don't laugh: a Reveal MusicStar from my childhood days) but I lost the cable and AC adaptor it came with a long time ago and need to find replacements, so until then, I've been playing by clicking keys with my mouse (which is extremely difficult...)