If you don't need hifi sound quality, ISD storage devices might be just what you are looking for. Goto:http://www.nuvoton.com/hq/enu/pages/default.aspx
and click "ISD Voice IC"
I have been using these IC's for many years for my talking coffee makers and robots. The quality is quite good.
For my coffee makers I always use ISD2560, as 1 minute is long enough to store quite some messages.
As far as I know (although I never used it), pitch control is possible using very little components.
Good luck, Eibert.