This is the Subtractor module. It is probably the most controllable module in the program. You can take any of three approaches: build from scratch, use a preprogrammed patch, or modify a stored patch.
The input controls are identical to those in the NN19 sampler. Review that page if you want some hints. The Mod Wheel is a bit more important in Subtractor, because the kinds of sounds that you might be designing here are more likely to use Amplitude Modulation or Frequency Modulation.
All of Subtractor's sounds are made with oscillators. Reason basically gives you two to work with. This would be limiting if these were like the kinds of oscillators available in the old analog studios. Fortuanately they are not; they are specially programmed to give you a lot of flexibility and good sound. Look at the top rows. You choose a waveform, an octave, and a transposition in semitones and cents. Don't worry about the octave for now, and remember that the transposition is there so you can detune an oscillator. What this means is: detuning an oscillator makes sense in a situation with two or more oscillators. One can be tuned so that it is in a ratio to the other, no matter what fundamental is played by the MIDI keyboard. A large ratio is like what we studied in additive synthesis. A small ratio can give the sound more depth. Listen for beating between the two oscillators.
The two knobs to the far right control relationships between the oscillators. Try adjusting them. You can use one to modulate the other's frequency, or you can control the ratio of each in the mix. The row labeled noise allows one to add noise to the sound. You control how soon the noise's envelope decays, the color--or how the noise is filtered, and the level.
The Mod Envelope controls a special type of envelope. You basically control the ADSR of one of the patch's oscillators or ratios. Experiment by setting a Mod Envelope and changing what parameter it controls with the round selectors at the left of the names of the osc's and ratios that it controls.
Finally, the LFO's allow you to control the timbre and evolution of the sound. LFO stands for Low Frequency Oscillator, and low in this case means sub-audio: below about 50 Hertz.
Not to over-simplify, but filters are important in a compact synthesis implementation because the sounds that you get from the oscillators are often rough or too raw to blend with other sounds, especially sampled sounds. Filtering can take the 'edge' off of the sound. You have two filters in series, but they are really intended to be linked via the link button at the top. You have 3 types: notch, HP, and LP--meaning band reject, High Pass, and Low Pass respectively. The 12 and 24 refers to a general frequency range: 12 being lower and closer to most of the energy in the spectrum. The "freq" slider gives you finer control over the center frequency, and the "Res" slider gives you control over how much attenuation or amplification occurs at that frequency. In the latter case, the solid white line in the center refers to unitary gain: no amplification or attenuation.