The Casio SA series is widespread and belongs to the 'single chip' generation, which was built starting the end of the eighties. The charming SA-1 is my favorite of the series, having the smallest buttons, but a great range of functions.
Besides the typical 100 melody and effect-sample sounds, it has 19 beats and 13 interesting accompanying loops (super accompaniment). I built in a controller that influences the CPU frequency. Charming and interesting random- and noise-loops are now possible.