The Analog Output Mikrokosmos II is inspired by Music Thing Modular’s Mikrophonie . Like that module, Mikrokosmos II has a piezo pickup attached behind the front panel, and the circuit amplifies the piezo signal and sends it to the output. There is a tactile scratch area on the front panel. You can use your fingernail or a guitar pick to scrape across it and generate output. It will also pick up sounds when you tap or thump on the synth case, plug or unplug cables, and so on. People have attached springs to the front panel, even a coil spring type doorstop. There are lots of possibilities.
There also is a jack for plugging in an external piezo pickup attached to a cable.
The first version of Mikrokosmos was a Kosmo conversion of the Mikrophonie circuit. Mikrokosmos II replaces that circuit with one based on a design by composer, performer, and instrument maker Godfried-Willem Raes. This preamp is designed specifically for piezo pickups and gives better frequency response than a typical constant impedance amplifier.