This chapter is conceived for music friends, who are not familiar with physics, especially not with (musical) acoustics. We describe the differences between sound, tone and noise. Then, with respect to the physics of sound, several important quantities are introduced (sound pressure, particle velocity, wave speed, just to mention a few). These have to be used for comprehending, in particular, the formation of standing sound waves on strings and in tubes, and what happens, when both ends of a tube filled with air are open or one end is closed. After these preparative parts, the construction of musical instruments and the way how they generate sound are discussed in a compact way. The structure and physics of typical instruments are explained: a recorder and a clarinet as examples for aerophones, a violin and its family representing the chordophones, timpani and drums for membranophones, bells for idiophones and a theremin and synthesizers for electrophones.