Synthesizer Expander Module is a free virtual instrument that faithfully recreates the classic Oberheim keyboardless synthesizer module from 1974. Designed originally as a companion to one of the first digital sequencers, this monophonic synth became a foundational piece in early polyphonic synthesizers. Renowned artists such as Joe Zawinul, Steve Porcaro, Styx, and Jan Hammer utilized its distinctive sound, making it a celebrated component in vintage synth history.

Though simple in architecture, this synthesizer is distinguished by its unique 12 dB/oct state-variable filter, offering lowpass, bandpass, highpass, and notch modes, which provide a rich tonal palette. The filter and an authentic Phasor effect have been meticulously programmed by award-winning designer Mark Barton, capturing the original character with precision. Additional features include ultra-accurate dual oscillators, extensive preset options for basses, leads, and percussion, as well as a studio-quality echo effect with tempo sync, all wrapped in an intuitive interface.

This plugin is available in multiple formats including AU, VST, VST3, AAX, and standalone, offering full MIDI control and DAW automation with easy MIDI learn and mapping. Its optimized DSP ensures smooth performance, with adjustable oversampling and zoom options for user convenience. As a free instrument, it presents an excellent opportunity to explore the sound of a legendary synthesizer. For those seeking expanded capabilities, a polyphonic version and modular bundles are also available separately.