A nice ressource is this page about modular synthesis. Its made for Nord Modular 1 but adaptable for other systems:
http://www.cim.mcgill.ca/~clark/nordmodularbook/nm_book_toc.html
Freqshifting is descriped here: http://www.cim.mcgill.ca/~clark/nordmodularbook/nm_spectrum_shift.html#frequ...
Cheers,
Malte