You can check SiON's preset voices. The key string to access SiONPresetVoice shows in left top letters. And you also can edit and save Voice MML. The comment text in the end of the first line is recognized as a name of your custom voice.

• [q]/[w],[2]-[8] ... Change the center octave
• [z]-[.]/[s]-[;] ... Play sound like a piano
• [down]/[up]/[PageDw]/[PageUp] ... Chaneg the voice number
• [left]/[right] ... Chaneg the voice categoly
• Mouse dragging on "keyboard" ... Play sound

• [shift]+[Enter] ... Switch the keyboard focus
• "New" ... Create new custom voice
• "Delete" ... Delete editting voice
• "Save" ... Save editting voice parameters in the flash cookie
• "Load" -> "Load MDX" ... Load voice settings from MDX file
• "Load" -> "Load OPM hex" ... Extract voice setting from OPM register's hex