dspic voice change
As I can see, Microchip dsPIC series is a mix between PIC and DSP, the result is very good. I can see that those dsPIC have much powerfull math instructions than TMS320 DSP, and have the very good functions of PIC like UART, SPI, AD, and more. The speed is only thing that is worst than Texas, dsPIC allows up to 30Mhz, versus TMS320 that are from 40MHz and up...
I think its not problem to synthetize voice on a dsPIC, you can make the PWM output to create analog signals, and implementing synthetize algoritms is not a problem using a C compiler. Speed is ok when you have samplerates of 8Khz, and 30MHz of clock, depending of complexity of your algorithm will consume more or less MIPS.