You can fit this miniature synthesizer in your wallet

The Tiny TS, the first standalone synthesizer from Jan Ostman, can do just that. Measuring in at a — as the name suggests — tiny 3.94 x 2.56 inches, it's roughly the size of a credit card.
The synth offers audio, CV, and gate outputs, and works well with Ostman's other synth chips if you don't like the way they sound. Despite the small size, it manages to fit in a full one-octave capacitive touch keyboard and six parameter knobs for controlling things like pitch and amplitude.The Tin