If you want a pocket-sized synth that's fun to play with, emulates '70s modular sound, and costs next to nothing, then check out the Korg Monotron Duo Ribbon synthesizer. With only five knobs and a ribbon keyboard, the Duo is easy to operate, but that doesn't mean it can't create rich, lush sound with its dual analog oscillators. The Monotron Duo boasts X-Mod circuitry that's based off of vintage Korg specimens, like its Mono/Poly design, and with built-in speakers, you can flesh out analog sounds on the go.