All project share the same fundemantal voice architecture shown in Figure 1 with only very minor differences. The only major difference across all six synth projects is in how the quad oscillator block is defined. All other aspects of the synth architectures remain the same.

Figure 1: SynthLab common voice architecture

Some notes about the voice:

all of the underlying theory for the module blocks is given in the synth book
the voice aggregates SynthModules from the same set of source code
you can easily generate smaller, light-weight and more CPU friendly versions of these synths by reducing the number of SynthModule components, while leaving signficant portions of the example code unaltered

You can find information about the voice throughout the programming guide including:
Engine & Voice Programming
SynthVoice Object
SynthVoice Example

The next section will show you the differences between each synth