The A-137-1 is a four-fold waveshaper (kind of four simplified A-136es in one box?).
Technical details can be found on Doepfer’s Homepage:
The example uses a single A-111 VCO (triangle output) which is controlled by an A-155 Sequencer. The A-137-1 has four modulation inputs: number of multiples, folding (distortion) level, symmetry of folding (i.e. positive and negative amount) and harmonics (additional harmonic created). Three LFOs (a slow, a medium and a fast one) and a S&H (synced to the sequencer) are used via A-138m matrix mixer to modulate the Wave Multiplier.
Here we go: