Musical pitch, also known as TONE or note, is the perceived frequency of a sound. It is determined by the rate of vibrations that produce the sound and is measured in hertz (Hz). TONE is the basic element of music, and it is used to create melodies, harmonies, and rhythms. Demo is short for demonstration, which is a performance of a song or piece of music. Demonstrations are often used to showcase a musician's skill and to give an audience a preview of a song before it is released.