In the code you posted, you basically use the exact same sample 3 times with the exact same settings (note and velocity) except for the seqPosition attribute used to set round-robins - so you won't be able to hear any difference.
In any case, you should have a different sample each time.
Also, you disabled the velocity tracking with ampVelTrack="0", so you should remove that.
What are you trying to achieve exactly?