City-ECG  r ythmic data  An organic growth principle  amongst several cities has been detected during the attempt of illustrating urban development in a ledgible way. Considering the city as a living organism, a new level of presentation of this almost human energy has to be found. This testing apparatus listens to the heartbeat of the city by reading four contemporary parameters: Noise, motion, wifi activity and carbon dioxide level. Dependent on the output of the sensors, the portable recorder tapes the data analog like an ElectroCardioGraphy machine (ECG) and punches it into paper.  The analog punchcards can be replayed by the corresponding drum-machine at any time and additionally enable a comparison of the different rythms.  "The city composes its own melody - music as a mode of communication in a time of 'big data'."