To set velocity ranges for the voice elements you have to go into the PC Editor. As you build up the composite voice with the necessary elements you can set the velocity ranges by going to the detail window for each, click on the oscillator tab and look to bottom right for the settings.

In the downloadable Ty3 reference manual page 17 there's a description of how to produce custom voices from scratch by importing wave files if you need it. If the elements you need can be found and imported from the preset voices it's usually a lot easier working with those - and no extra sample memory (DIMMS) needed.

John