Thanks for the explanation Melanie...I only want six becuase some idiot went & designed a guitar with six strings (I reckon every instrument should be created using the banjo model ....then it's be a doddle to use my humble PIC16F690 with it!)

aratti, thanks for the info...i'm not sure that'll be helpful in my scenario, as I need to vary the PWM duty cycle per pin output (whereas that schematic uses one common PIC PWM output stream & then just 'ands' it to suit)