Music transcription allows to convert an audio recording to musical notation through mathematical analysis. It is a very complex problem, especially for polyphonic music - currently existing solutions yield results with approx. 70% or less accuracy. In the talk we will focus on transcribing a monophonic audio input and see how we can modify it on the fly. To achieve that, we need to determine pitch and duration of each note, and then use these parameters to create a sequence of MIDI events. MIDI stands for Musical Instrument Digital Interface and it encodes commands used to generate sounds by musical hardware or software. Let’s see how to play around with sounds using Python and a handful of its powerful libraries. And let’s do it in real-time!