UsefulSynthCircuits has introduced a mod for the classic Oberheim SEM Synthesizer Expander Module that expands its synthesis capabilities with two octaves of sub bass.

Here’s the official demo:

Note: The mod is a simple DIY project, but does require basic soldering.

Pricing and Availability:

The SEM Sub Osc Module (1974 – 1979) is available now for $45 USD.