PyPiano maps computer keyboard input to synthesized piano notes and provides a visual keyboard. Its variants explore both ordinary window input and listening for keys while another window has focus.
KeyBored is a related musical-keyboard prototype with a browser interface and a Python version. They are separate implementations of the same simple interaction: use keys already on the desk to play notes.
Keyboard capture depends on the operating system and window setup. These are small input and sound experiments, with different interfaces rather than a single packaged music application.