Read the staff. Play when ready. The app follows.
No MIDI keyboard handy? The computer keyboard plays too:
Q W E R T Y U I O P C5 D5 E5 F5 G5 A5 B5 C6 D6 E6 A S D F G H J K L ; ' C4 D4 E4 F4 G4 A4 B4 C5 D5 E5 F5 Z X C V B N M , . / C3 D3 E3 F3 G3 A3 B3 C4 D4 E4 Shift+key = sharp [ / ] = octave down / up Chords: hold keys together (e.g. Z+Q = C3+C5)