The pitchshifting without changing time is what the V-synth is all about.
All you have to do is to record or import your sample, encode it (tell the V-Synth the original tempo and select one of the algorithms to analyze it like solo, ensemble, or backing and hit execute)
Then you create an init patch, select PCM for OSC 1 and select the user waveform you created from the waveformlist.
Make sure that the variphrase option in the PCM oscillator screen is active and bingo. You can play the sample all over the keyboard with no tempo change.
Of course the really useful range is limited to something like an octave maybe two. Further than that you will get artifacts but htose can sometimes sound really cool.
If you select the time sync feature in the PCM oscillator screen the sample will sync to the patch tempo or the midi clock and if you used the SOLO mode while encoding even the formants will be preserved so you dont get the chipmunk artifacts when transposing the sample upwards.
Solo encoded samples allow you to activate the robot dunction that eliminates all pitches in a melody. Sounds robotic but allows you to totally change the melody in a vocal phrase.
In any case you should try the legato function with vocalsamples (you can activate that in the PCM oscillator page as well).
When you play legato style(without lifting your fingers from the keyboard while playing a line) you can also superimpose new pitches unto a sampled melody.
Hope that helps.
If you have any more questions feel free to ask. I know this thing inside out.
If you want to i can mail you a patch that has everything already set up so you only have to do the import your own sample part.