Making a synth sound “fatter” and more analog
Alright, there will be one time or another, where you might want to take a synth sound and make it sound fatter and more analog. This kind of sound is difficult to reproduce in soft synths. Most quality digital soft synths, try to have their own distinct digital sound, leaving analog-like sounds to dedicated analog emulation synths.
One of the best emulations I have heard is Arturia’s Analog Factory. Another one is Admiral Polyanna. Native Instrument’s Pro – 53 is also very good. Finally, Spectrasonics latest achievement, Omnisphere, contains many analog sampled waveforms.
Arturia Analog Factory
However, there will be times when you want to create your own analog emulation, or try to make a sound even better. First of all, you should know that you have to choose the right synths for the job. Not all synths are really for this kind of of task. If you have been trying for over 2 hours to make something sound good, but you can’t, chances are that you are using the wrong tools 
Now, let’s get to the point. To make a sound fatter, you need to have some kind of dissonance in it. First of all, don’t use sine waves, because they contain only one harmonic: the fundamental. We want harsher waveforms. We have to use square or saw waves.
A powerful tool to cause dissonance is pulse width modulation (PWM). This constantly changes the width of the square wave, which translates into a more dissonant sound.
The second way to create dissonance, is through the tuning of our oscillators. You can lower and raise them by a few cents, in order not to be in tune. Additionaly, if you want a bass sound, you should lower all of them, or some of them, an octave.
So, this was really the basic idea! Now, to make the sound fatter, you can use effects. Chorus is a good idea, because, slight amounts of it are not very noticable, but make the sound more dissonant. Distortion is always an option, but you might want to use a good VST effect, because most distortions built in soft synths might not be the best option. Finally, if your sound is not as good as you wanted it to be, you can always layer another sound on top of it! You can also add reverb, which helps to make every sound more organic, even though reverb is the most abused effect, because it can improve any sound.
