Using the Parameters

The follow information has been obtained from Vocaloidism; VOCALOID Tutorial – Using the Parameters

Vocaloid Adjustments
Adjust the length of consonants. Large adjustments doesn’t do much, so usually people doesn’t adjust this value very much.
 * VEL （Velocity）

Adjustment of the volume. This is probably the most important parameter out of all of them.
 * DYN （Dynamics）

Control of the weight of the voice’s breathing. Will considerably effect various nuances. Volume will also be adjusted.
 * BRE （Breathiness）

Adjusts the “brightness” of the voice. This also adjusts volume.
 * BRI （Brightness）

Sharpen the voice. This parameter can make quite an impression, so don’t adjust it too much.
 * CLE （Clearness）

Reproduce the variation of pronunciation through adjustments of the opening of the mouth. This will also change volume.
 * OPE （Opening）

Adjusts the voice to a more male or female feel. Works to not break the original foundation of the voice.
 * GEN （Gender Factor）

Adjustment of the Portamento’s starting position. Here’s a definition of Portamento. “A technique of gliding from one note to another without actually defining the intermediate notes; a smooth sliding between two pitches. This term is used primarily in singing and string instruments. Often called glissando for other instruments, especially the trombone.”
 * POR （Portamento Timing）

Adjustments the pitch. Required for the removal of certain nuances.
 * PIT （Pitch Bend）

Adjusts the width of the pitch bend. Use this a lot to match the pitch bend.
 * PBS（Pitch Bend Sensitivity）