SEMS stands for “Sample-based Electronic Music from Scratch”. To make such music, you primarily use Audacity. You will need the LADSPA plugins bundle and working Nyquist plugins, both generators and effects. Basically you generate a sound in the form of a sample, then, if you want a more unique sound, apply some ladspa and nyquist effects onto that sample. Make sure they alter the sound in quality. Then when you done, export every sound in wav. It is recommended to create music with only such samples in mod trackers like MilkyTracker, FastTracker II, OpenMPT etc. I personally put them in OpenMPT. You can also use Wavosaur to apply effects to samples. You can also draw samples in the Sample Editor in OpenMPT. Then you can apply some effects to those samples inside the OpenMPT sample editor or you can import samples into Audacity and apply ladspa and nyquist effects like you’d do with audacity-generated samples.
I apologize if you didn’t understand sh!t, i’m not sure how else to explain this genre…