Every sound produced by a musical instrument has a physical explication, the way instruments are created and the type of materials that are used define in a unique way the resulting sound.
The sound wave is a transfer of energy that doesn’t imply matter.
Within a more theoretical approach, sounds are Mechanical Longitudinal Waves. So, musical instruments and Physics are intimately related. How can they coexist? There is a mathematical formula that actually explains music, starting from the musical instruments and the Physics’ properties. The wavelength of the sound is defined as an interval between two points where the sound doesn’t have a repeated behavior. The period (T) represents the shortest interval where the wave behavior doesn’t repeat. Hence, the total number of vibrations the sound will realize in one second represent the “Frequency” (f).
Every sound travels at a specific speed depending on the wavelength and the frequency, so the same instrument can produce quite an interesting process. Interference is another thing that must be discussed when analyzing musical instruments and in the Physics context. It is very probable for two sounds to be present simultaneous is the same place at the same time. The effects of combined waves are usually analyzed using the Superposition theory.
To put it in a simple way, imagine two identical musical instruments in a standard Physics experiment. Let’s say they are two trumpets. If they are blown at the same time, on a certain frequency, the result may give you a headache. When the crest of two waves meets the result is usually annoying for the human ear, the resulting phenomena are called destructive interference.
Furthermore, it is good to say that after passing the intersection between the waves they will return to the initial form. Most people have no clue about what it is going on behind the magic of music. The relationship between musical instruments and Physics comes more like a curiosity for most of us, who are ignorant of the rules of Physics phenomena. Yet, such information is crucial for those who make the instruments as such.
The most relevant to our knowledge is the intensity of the sound. This is also part of the relationship between musical instruments and Physics. Our hearing capacities are those that determine the intensity of the sound at a very subjective level. Otherwise, Physics uses a standard scale to measure the way sounds in the surrounding world touch upon our auditive system.