Time stretch/compress vocals

I was wondering if anyone had any tips for time stretching/compressing vocals. I have been using Soundforge and get ok results if i don’t exceed a 10% increase on compression and so so results on stretching.but I almost always hear anomylies and the vocals don’t souond natural. Is there a different app I should be using? Or a technique I should be applying? Any help would be greatly appreciaited.

Thanks a million

Wow. You guys have been great. I picked up Melodyne the other day and it is amazing. It stretches/compresses beautifully.Carlos, I appreciate your input on that mix on my very much neglected site . It was done a LONG time ago. Unfortunately, my skills have not improved much since then. I’ve tried a couple of things since then and I’ll try to post a link to them soon. Thanks for all your help.