The XFM2 is an FM -- or frequency modulation -- synth. This digital architecture, which was popular in the '80s, sounds dramatically different from the typical analog setup of two oscillators and two filters. It fell out of fashion quickly, so there aren't that many hardware-based FM options on the market, making the XFM2 an attractive option.

For such a tiny synth, the XFM2 has a lot to offer. It has six operators (which function somewhat similarly to analog oscillators) and is capable of 64 voices. Two patches can either be played simultaneously or as a keyboard split. It also has plenty of built-in distortion, modulation and time-based effects.

Software emulations of the most iconic FM synth -- the Yamaha DX7 -- sound pretty darn close to the original hardware. But for musicians who want to avoid using soft synths -- and have some soldering skills -- the XFM2 might be worth checking out.