The pitch and rate of many of the TTS voices might also be dependent on their internal programming but many of them can be adjusted as Cyber suggested.
Programs usually come with the voices from their respective manufacturer to allow the end-user to adjust the voices but one program doesn't work on all voices.
The Text Aloud program is pretty handy with testing the voices as are several others. The Balabolka program is no longer needed unless one is still running XP!!
![Grin ;D](http://www.ultrahal.com/community/Smileys/default/grin.gif)