The EHX Micro Synth is designed to sound like a guitar synthesizer without requiring a special guitar synth pickup, and replicates "fat analog synth" sounds. It has 10 sliders for various settings, including low/med/high octave, square wave, attack delay, and filter sweep settings. This was used in the end of Cherub Rock with an old brown Maestro Fuzz tone.
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A close-up pic of the Micro Synth was also used in an October 2, 2014 entry on SP Nexus.