Abstract: A system for transcribing a sequence of input analog signals having characteristic frequencies and durations into indicia which visibly reflect the frequencies and durations of the input analog signals. The system uses the principles that the frequency of an analog signal can be determined from the number of zero crossings the signal makes in a predetermined time period and that the durations of the input analog signals can be determined from the number of successive time periods that the determined frequencies remain the same.In the preferred embodiment, the system transcribes successive musical tones into corresponding musical notes. A microphone produces electrical signals corresponding to the musical tones and a frequency digitizer circuit produces a digital signal train comprising a digital pulse for each zero crossing of the electrical signals.