Charlie, with all due respect for your question, the biggest way
you can improve your vocals is by practice not programs!
One fine book is "Set Your Voice Free" by Roger Love,
and it includes an exercise CD. He's probably the most sought
after voice coach in the recording industry right now so he might
be doing something right in helping singers.
Never tried Antares Autotune (pitch correction) BTW, however,
you may want to check into that. Best of luck...
P.S. If you're already taking lessons and/or doing exercises,
hope you don't mind how basic my advice is!
