Here is a list of the mods on my SK-8:
Phat Philter Bank - polyphonic VCF filter with CV input and resonance
Slo-AD mod - changes the attack and decay rates of the preset and samples sounds
Pitch Wheel mod - add a pitch bend wheel to the instrument sounds - like a real synth wheel
Memory Expansion Mod - expands the sample memory by 32x
Memory expansion display - 2-digit LED readout and bank select for the 32x expansion
Instrument individual out mod - individual output for each of the 4 polyphony voices, without drums coming through
Instrument Stereo mod - creates a true stereo panning output for the instrument and sample voices
LFO mod - add an LFO vibrato to the instrument and sample sounds
Drums filter bank - likewise but for the drum rhythm sounds
Drum pitch mod - changes the drum pitch by +/- 1 octave
Drum swap mod - swap the different drum sounds with others in a rhythm
Drums out mod - separate line out for drums only, without instrument sounds coming through
Drum trigger mod - trigger the 4 drum sounds on the SK-8 independently (like the SK-5)
MIDI mod - MIDI IN interface for the instrument sounds and drum sounds - SK becomes a sound and drum module for external sequencer
Others available but not tried by me:
DIY preset ROM sounds - replace the preset ROM instrument sounds with your own sounds
Program Change mod - change the instrument sounds and drum rhythms externally by MIDI
Most of these are mentioned here on this forum but the original guides are on the Yahoo groups SK forum:
http://launch.groups.yahoo.com/group/CasioSK/Cheers, Graham