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What makes something a musical instrument 

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What makes something a musical instrument 

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What are musical instruments? what is it that makes something an instrument? basically its any object that can be used to create sound, which is most objects in existence, the key feature is that it does actually exist, but that's quite a broad explanation, some other guys gave a much better explanation and categorised them.....read on.

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Erich von Hornbostel was more than a Joe Wilkinson impersonator, he and his mate Curt Sachs pioneered the field of organology which is the study and classification of musical instruments, These two weird beards had loads of time on their hands and decided to divide all musical instruments into different categories, known as the Hornbostel-Sachs classification system. There are 5 main categories of musical instrument identified by Hornbostel-Sachs which are, Idiophones, Membranophones, Chordophones, Aerophones and later electrophones. All of the broad categories of classification also have further sub categories, It would be almost as pointless to try and cover them all as it would be boring so I will give some specific examples.

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"Idiophones primarily produce their sounds by means of the actual body of the instrument vibrating, rather than a string, membrane, or column of air. In essence, this group includes all percussion instruments apart from drums, as well as some other instruments. In the Hornbostel–Sachs classification, idiophones are first categorized according to the method used to play the instrument. The result is four main categories: struck idiophones (11), plucked idiophones (12), friction idiophones (13), and blown idiophones (14). These groups are subsequently divided through various criteria. In many cases these sub-categories are split in singular specimens and sets of instruments. The latter category includes the xylophone , the marimba , the glockenspiel , and the glass harmonica."

A simple example of an idiophone are cymbals, as described above what makes cymbals an idiophone is the fact that the whole body of the cymbal vibrates to create the sound. Cymbals fall into the concussion sub division of of struck idiophones. Cymbals are made up of two main parts, the dome in the centre and the bow which is the rest of the surface area of the cymbal. the dome makes a higher pitched bell like sound when struck and the bow is referred to in two separate parts being the ride area, which is the thicker part closer to the dome and the crash, which is the thinner part of the cymbal towards the edge. Bigger and heavier cymbals are louder with longer sustain and thinner cymbals have a lower pitch when struck. The timbre of a cymbal varies greatly depending on the material it is made from, its size and how it is struck. for example a high hat struck with a brush will have a softer but more complex colouration than when hit with a stick, this is down to the envelope of the sound being played which is basically adsr, attack- is how quickly a sound reaches full volume after the note is struck, decay- is how quickly the sound drops to the sustain level after its initial peak, sustain- is the constant volume the sound makes until its release and release- is how quickly the sound fades when the note ends, so a cymbal struck with a stick will have a quicker attack, longer decay, sustain and release time than when hit with a brush because because of the harder connection with the cymbal more energy and vibration is created, providing they are struck at the same velocity ofcourse. The reason for the difference in timbre and sound is basically down to how it vibrates and moves air about and transfers acoustic energy to your ears.

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"Membranophones primarily produce their sounds by means of the vibration of a tightly stretched membrane. This group includes all drums and Kazoos."

Snare drums are a membranophone, hence the tightly stretched membrane or head across the frame, a snare drum actually has 2 heads, one on top and one on the bottom of the drum. there are wires on the bottom of the snare drum which are actually called the snares which give the snare an almost rattle sound. Snares don't have a definite pitch and can be hit with sticks, brushes, hands etc, they can be struck on the head, the rim or the side to give different sounds. snares have a sharper higher pitched cracking sound compared to the toms and bass drums on a drum kit.

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"Chordophones, which are arguably the most common, and most popular, of all musical instruments, primarily produce their sounds by means of the vibration of a string or strings that are stretched between fixed points. This group includes all instruments generally called string instruments in the west, as well as many (but not all) keyboard instruments, such as pianos and harpsichords."

Pianos are Chordophones, a lot of people won't recognise them as a stringed instruments as they are played with keys, however the keys operate hammers which strike strings inside the body of the piano, when the strings are struck they vibrate through a bridge to the soundboard which amplifies the acoustic energy through the air.

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"Aerophones primarily produce their sounds by means of vibrating air. The instrument itself does not vibrate, and there are no vibrating strings or membranes."

Interestingly a whip....yes you heard me right! just like Indiana Jones. A whip is a type of aerophone because it creates sound by disturbing the air, specifically it is a displacement free aerophone according to Hornbostel-Sachs. this means when the airstream meets a sharp edge a periodic displacement of air occurs to the alternate flanks of the edge,. in layman terms, the whip doesn't make a sound resonate frequencies itself, it causes sound when moved quickly through the air, that how that swishing sound occurs, it's the same as a blade or cane being swung through the air, it causes the air to move around the object

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"The fifth top-level group, the electrophones category, was added by Sachs in 1940, to describe instruments involving electricity. Sachs broke down his 5th category into 3 subcategories: 51=electrically actuated acoustic instruments; 52=electrically amplified acoustic instruments; 53= instruments which make sound primarily by way of electrically driven oscillators, such as theremins or synthesisers, which he called radioelectric instruments."

The minimoog below is an example of a synthesiser and an electrophone which falls into the 3rd category of electrophone (53) in that it relies solely on electricity to create sound and can't without it.

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So for example the reason that 2 chordophones might sound different playing the same note I have looked at below by stealing a well referenced example from the internet.

the top graph shows a guitar playing a d4 and the bottom shows a piano playing the same note.Observe the relative strengths (read shape) of the peaks of the first few harmonics. The guitar (top graph) has a taller/stronger fourth harmonic and the piano (bottom graph) has a taller/stronger second harmonic. shows that although the musical note played in both cases is the same, they are being played by different musical instruments.

So the shape and body of an instrument gives it its unique quality even though they share the same fundamental frequency. each note is made up of harmonics so shapes and sizes of the instrument and how it is struck will shape which harmonics are emphasized.

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Explain the acoustical properties of sound generators and resonators

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Explain the acoustical properties of sound generators and resonators

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Assess the impact of physical form on the sound of an instrument

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Assess the impact of physical form on the sound of an instrument

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https://en.wikipedia.org/wiki/Hornbostel–Sachs#Aerophones_(4)
https://en.wikipedia.org/wiki/Piano
https://www.quora.com/What-is-the-difference-between-the-same-note-played-by-a-guitar-and-a-piano-How-is-that-reflected-in-the-sound-waveform