We may not all like the same music but we can agree on which sound is music and which is noise. Noise is not a pleasing sound because the wave patterns are random. When the wave pattern is regular we hear pleasing sounds that we call music. Each instrument has a distinct sound that is called the quality of tone. This quality lets us distinguish between a violin and a tuba.
2. Music and Instruments
Instruments produce standing waves to make what we call music. The class of instrument is based on how the standing wave is produced. Stringed instruments make sound with vibrating strings. Wind instruments make sound with a vibrating column of air. Percussion instruments make sound with vibrating materials such as a drum head.
3. Fundamental Tones and Overtones
Instruments produce standing waves at certain frequencies. For example a violin string is fixed at both ends. When the string vibrates at its lowest frequency, it will have only one crest. This is called the fundamental tone. The first overtone has a higher frequency and will have a crest and a trough. The second overtone has two crests and a trough. When instruments play music together, the fundamental tones and overtones blend together.
When a violin string vibrates, the wood of the violin will also vibrate at the same frequency. This makes the music louder. This vibration is called resonance. Every material has a natural frequency that will cause resonance. Resonance is also how an opera singer can shatter a glass. If the singer can produce a sound at the natural frequency of glass, the glass will resonate and shatter.