i wouldn't.
at some point there is little gain in thd/aliasing between full 16bit 64k entry and fewer entries interpolated between them (even linearly)
especially if you have a big number of those sinewaves to be mixed together and you use fixed point math. dspic doesn't have hardware floating point, but 40bit (9Q31) fixed point.
let's say you don't do a full manual, "only" 64 sines total, 44 key keyboard.
you really need 64 phase accumulators with sligthly different tunings per octave or you end up with standing waves if you cheat and only use 12
each drawbar has to mix up to 44 sines and then you have to mix the (up to) 9 drawbars together
It's impressive if you manage to pull it off
but i don't see it happening if you have to fetch randomly from flash each time (5 intructions cycles, plus the preparing) or from external memory
perhaps he has a different approach to this problem but this is how you'd have to do it with a single processor
just saying, HOAX: Hammond On A Xilinx (FPGA)