As was suggested earlier, change the key to match your vocal range. We have to do this with many of the songs that we perform, and if you are careful about whether you transpose up or down depending on the instrumentation you will find that this works well for you.

I haven't used the TC Helicon built in harmonizer feature in a long time so I don't recall for sure. But if there are settings for "humanization" you could experiment with those to see if it improves the harmonies.

Also, based on our experience, you have to do a lot of practice with any kind of vocal harmonizer in order to get the best results.

We currently use two TC Helicon VoiceLive2 hardware harmonizers in our duo, and they are able to produce some very realistic harmonies. This is not an inexpensive solution, but it does work quite well. You can sometimes find a good deal on eBay.

I should note that it took several months of working with the harmonizers before we were able to approximate some of the demos that TC Helicon does at trade shows, but the harmonies that we produce now are very realistic, and are crowd pleasers. Early on the harmonies were not that good.

I would experiment with any humanization settings that might help your harmonies sound less mechanical. The other thing is that, as far as I know, the TC Helicon software implementation that PG Music is using probably has not been updated for quite some time and I expect that TC Helicon has made significant advances as can be seen by their more recent hardware offerings.

Hope this helps,
Burt