Sounds of Music

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Sounds of Music is an event in which two participants build one homemade instrument, play a scale on their instrument, complete a volume score test, and explain the physics of sound through a written test.

The Instrument

The main part of Sounds of Music is the building of the instrument. You will need to build one durable, original, and creative instrument with which you will play a scale. You will also need to answer questions about the theory of your instrument and how you built it.

Building an Instrument

For 2019's competition, participants are required to build one instrument of any type, barring electrophones. The instrument must be played in such a way that all energy put into the instrument to make a sound must originate from the team. This differs from rules prior to the 2019 season, which had competitors building two instruments.

When building your instrument, you'll have to be creative. No commercially available instrument parts are allowed, (i.e. mouthpieces, mallets) excepting strings. Experiment with different materials. PVC pipe is a common material that is cheap and easy to make into an instrument; PVC pipe aerophones are very common.

Other instruments very commonly made include idiophones (xylophone, marimba, etc.). You will also want to experiment with materials if you are building one. Try different types of metal pipes and different types of wood to see what works best. There are several resources online that will give you the exact length to build the bars, but you will need to fine tune these so you get the exact pitch.

When building a idiophone or other percussion instrument that is hit, you will also need to consider the material with which you build the mallets. If you use a soft material such as rubber or yarn, the percussion instrument could be drowned out by a wind instrument. If you use harder materials, the instrument will have a harder, clearer tone, but the tone quality may suffer. Once again, you'll have to experiment to see what suits your playing style best.

Remember that your instrument MUST be in the allowable range. For the 2018-2019 season, the range of the instrument must be from F2 to F5. See this page for more about determining pitch.

There are four basic classifications of instruments under the Hornbostel-Sachs system as shown below. The fifth, electrophones, was not included for several years after the creation of the Hornbostel-Sachs system and is not used in competition.


An idiophone is a instrument in which the vibration of the instrument itself is what creates sound. They are generally the percussion instruments that are hit, shaken, or rubbed to create sound. Resonators can also be added to these instruments to create a sound.

In this event, the major type of idiophones created are xylophones, marimbas, or chimes. When you double the length of a bar, you cut the frequency in a fourth (put it down two active octaves). So in these instruments, to go down an increment of the scale, you must decrease the note length by a factor of the 24th root of 2. These also require you to fine tune (sand/file).

Examples of idiophones include

  • Xylophones
  • Bells
  • Steel Drums
  • Wine Glasses


Membraphones are instruments which have a vibrating membrane over a resonator to create sound. These instruments are generally harder to build and perfect.

Examples of membranophones include

  • Tuned drums
  • Timpani
    • Kazoo (Note for the 2018-2019 season, the rules do not allow for making an instrument that requires participants to sing or hum into it, thus a kazoo is not allowed.)


In aerophones, sound is produced by a vibrating column of air within the instrument. The air is usually produced in one of two ways: the player directs wind towards a sharp edge, creating an oscillating wind going in and out of the pipe; or, the player buzzes his/her lips against a mouthpiece, creating a vibrating column of air that goes into the pipe. The wind that goes into the pipe vibrates, creating a sound wave. Pitch is changed by the changing size of the column of air.

Examples of aerophones include

  • Flutes
  • Pan Flutes
  • Tubas
  • Trombones
  • Horns/Trumpets


In chordophones, sound is produced by a vibrating string. The vibration of strings produces standing waves producing fundamental frequency as well as harmonics (the relative abundance of these make up the timbre of your instrument). Resonators added to the string will enhance the sound by vibrating sympathetically with them.

In chordophones, the wavelength made is twice the length of the string. Since we know that velocity equals frequency time wavelength, after assuming that the velocity of sound in the string will remain constant, we find that when one doubles length, frequency will be cut in half (note goes down an octave). Because the relationship between length and frequency is exponential we know that for every increment one goes up in a scale (1/12), the note increases by a factor of the 12th root of two. You can use this fact for starting your tuning. Unfortunately, you'll need some fine tuning and many hours to get your instrument to play accurate notes due to imperfections in string and to the fact that there will be different amount of tension on different strings (when playing different notes on single guitar string, there will be different amounts of tension). This will result in different velocities of sound in the string, making this form of tuning less reliable.

Examples of chordophones include

  • Guitars
  • Violins
  • Harps
  • Zithers
  • Lyres
  • Piano/Harpsichords (on the harder side to make, not advised)


NOTE: Electrophones are not allowed under the rules for 2013 and beyond.

Concerning electrophones, sound is produced by an electrically powered oscillator. It is highly unlikely anyone will build this type of instrument for Sounds of Music anytime in the near future, and it is also barred from competition under 2013 rules.

Examples of electrophones include

  • Theremins
  • Synthesizers

The Competition

While much of the work for the Sounds of Music event takes place before the competition, in the form of building, tuning, and practicing, only one part actually counts for Science Olympiad, and that is the competition.

This section is not a replacement for the Science Olympiad rules manual. Please read the Science Olympiad rules manual to get exact and official descriptions of each section.

The Written Test

The most points are given for the written test. In a separate room from the instrument testing area, you will have at least 20 minutes to complete at least three questions from each topic:

  1. Principles of acoustics
  2. Science terminology involving sound and its production
  3. Fundamental elements of musical sound; perception of it; resonance
  4. Design and function of instruments
  5. Notes, scales, and intervals (music theory)

The Setup

When you arrive in the competition room, you will have two minutes to set up. This normally isn't a problem, as most instruments are mounted or otherwise ready to play. Some teams do bring xylophones that are not mounted or otherwise connected, and these teams will likely use the majority of the time. The room will likely have very few resources. Some competitions may provide a table or desks to place xylophones on, but it may be smart to bring your own portable table just in case. When setting up, competitors and their instrument have to be 1 meter away from the testing equipment, and failing to do so may result in a penalty.

During the setup time, introduce yourself to your judges. Provide information such as your name, your school name, the type of the instrument you created, and the scale you will be playing.

The Pitch Test

The main testing component will be a pitch score test. You must play a major scale - any major scale - and hold each note for five seconds. If you wish to skip any notes, you must declare that beforehand. You will be scored per note. Multiple attacks on each note are allowed, and the average pitch on each note counts for the score. Two apps were recommended by Soinc for measuring pitch in this event: Google Science Journal and Accord Chromatic Tuner (only available on Android).

The Volume Test

The volume score test will involve playing a single note from your scale for five seconds. Multiple attacks are allowed. The highest volume in decibels at a distance of one meter will count for the final volume. If the instrument registers a volume louder than 85 decibels, the volume test will end and 85 decibels will be recorded.

The Log

The last portion of the event is the log score. You must submit logs containing a list of materials used, a chart showing how you tuned (with at least 5 data points), proper labeling, and a diagram that shows how the instrument is played.

Rubric Overview

The highest score possible for this event, according to the rules, is 100. 36 points are awarded in the pitch test, with a maximum of 4.5 points per note. 10 points are awarded for logs. 9 points are awarded in the volume test, and 45 points are awarded for the written test.

Written test topics

Sounds of music tests jump from topic to topic depending on the test writers. While the physics of sound is guaranteed to surface, tests have in the past borrowed anything related to sound from a broad umbrella of disciplines beyond merely physics. Both partners should expect to study a variety of content beyond physics, music theory, and instrument building. With this in mind, it is important to not lose motivation because of random questions, as most teams will also face comparable difficulties in grasping seemingly random content.


From the music of a concert, the creak of a door, to the gusts of the w ind, sound permeates our world. This is true quite literally—sound occurs when molecules of air vibrate, jostling and pushing against each other. By vibrating, these molecules hit neighboring molecules, which in turn hit and bump their neighbors into vibration as well. This molecular chain continues to radiate outward from the original source, and, if the vibrations find their ways to our ears, we may hear it as sound.

This process of vibration is a form of a wave. A wave that propagates through a physical material has a wavelength, frequency, and speed. The wavelength ([math]\lambda[/math]) of a wave is the length traveled by the wave before it repeats itself. The frequency ([math]f[/math]) is the number of times the wave repeat in a given time. For instance, if 15 wavelengths of a wave pass by a point in 3 seconds, the frequency there will be 5 cycles of the wave per second, or 5 hertz, which is the SI unit of frequency. Wave speed ([math]v[/math]), as you probably guessed, is the rate of distance traveled per time. These three quantities are related by the equation [math]\lambda f=v.[/math]

Sound waves in air are longitudinal waves, which are defined by motion of the wave parallel to the motion of the medium (the particles that transfer the wave). Longitudinal waves are not the only type of wave vibration. There are also transverse waves, where the motion of the wave is perpendicular to the motion of the medium. Some media are even capable of carrying both types of waves, like a Slinky. It is worth being aware that transverse and longitudinal waves are not the only type of motions undertaken by a wave—water waves are neither transverse or longitudinal, as particles move in both the perpendicular and parallel direction.

Propagation of a longitudinal wave
Propagation of a transverse wave

Physical quantities of sound

  • Pressure (p): pressure is defined as the force applied per area. The pressure exerted by all of Earth's air upon the ground, or atmospheric pressure, is 101325 pascals. Sound, though, causes fluctuations in the pressure in some regions of air because of the bumping and vibrating of air molecules, so there may exist a pressure difference from atmospheric pressure
    • The maximum value of this pressure difference is known as the pressure amplitude
  • Displacement amplitude (A): the maximum value that any single particle displaces in a sound. Displacement amplitudes always occur at points where the pressure difference is zero, because particles are densely packed together at regions of high pressure, so they are less capable of bumping past each other, and thus less capable of displacing.
  • Power: power is rate of change of energy with respect to time.
  • Intensity (I): power transmitted per area receiving energy; that is, [math]I=\frac{P}{A}[/math]. Most of the time, you will use the formula [math]I=\frac{P}{4\pi r^2}[/math] on sounds of music tests, where [math]r[/math] is the distance away of an observer from the source. This equation results as a point source radiates sound uniformly in every direction, implying the energy is transmitted onto the surface area of a sphere. However, in the case of a directional source that only emits sound in front of it and none behind, the proper equation is [math]I=\frac{P}{2\pi r^2}[/math], with a two in the denominator, as the sound only covers half a sphere of area. In reality, it is very rare to find a source that perfectly emits sound only in the direction covered by half a sphere. On tests, if you are in doubt, use the equation for a point source that radiates sound spherically and omnidirectionally.
  • Speed: the speed of sound changes based upon medium. Sound is fastest in solids, then in liquids, and slowest in gases. Some equations for the speed of sound are given below.
[math]v = \sqrt{\frac{B}{\rho}}[/math] in a fluid with bulk modulus [math]B[/math]
[math]v = \sqrt{\frac{Y}{\rho}}[/math] in a rod with Young's modulus [math]Y[/math]
[math]v = \sqrt{\frac{\gamma R\mathcal{T}}{m}}[/math] in an ideal gas with adiabatic constant [math]\gamma[/math], temperature [math]\mathcal T[/math], and molar mass [math]m[/math]
[math]v = 20.05\sqrt{\mathcal T}[/math] in air at temperature [math]\mathcal T[/math] in Kelvin

Music production

For musical instruments with a definite pitch, making music requires the capacity to generate a a pitch and sustain it long enough for the human brain to interpret it as potentially musical. All pitches are associated with a frequency, which the instrument must produce. Most instruments can produce a variety of frequencies for a singe pitch. Often, but not always, the frequency you hear is the fundamental frequency, which is the lowest of the frequencies produced. The frequencies are higher than the fundamental, and so we accordingly call them overtones.

The frequencies at which standing waves can occur (i.e. overtones plus the fundamental) are collectively called partials. If all partials are integer multiples of the fundamental, we may also call them harmonics. We denote the [math]n\text{th}[/math] harmonic with [math]n[/math], where [math]n=1[/math] is the fundamental frequency. The reason for overtones is that standing waves of different lengths can be fit onto a single musical instrument:

String harmonics.gif

  • Waves on a string of length [math]L[/math] and linear mass density [math]\mu[/math] under tension [math]T[/math]
[math]f_n = \frac{nv}{2L} = \frac{n}{2L}\sqrt{\frac{T}{\mu}}[/math]
  • Air column of a pipe with both ends open
  • Air column of a pipe with one end closed and one end open
Only odd [math]n[/math] exist for such a pipe.

We usually refer to pipes with both ends open as open pipes, and pipes with exactly one end closed as closed pipes.

Overtones, if present, are much like the fundamental in that they carry energy as they travel through the air into your air. When a band of overtones with close frequencies all carry a high energy, this high-energy region is known as a formant. Beyond instruments, formants are extremely important in speech production (this is intuitively reasonable as the human voice is a musical instrument, equipped with singing abilities). Indeed, you will be more likely to encounter the term "formant" in the acoustics of speech and singing than in the acoustics of non-voiced musical instruments.

Sound phenomena

Interference/superposition - Sound waves, when encountering each other, will undergo interference. This means that at every point where both waves overlap, the pressure difference there will equal the sum of the pressure differences of the individual sound waves. Since it's as though we have added the waves on top of each other, we also call this the principle of superposition.

Constructive Interference.png Destructive Interference.png

Two loudspeakers with the same input can serve as a demonstration of interference. When both loudspeakers are placed a distance of two or more meters apart and both play a single pure tone, the room will be filled with bands of loud regions and soft regions. Many classrooms today are arranged with such a system of two loudspeakers connected to a single computer, and if your Science Olympiad coach has such a classroom, you can ask them to help experimentally illustrate this effect. The outcome will resemble the image below.

Loudspeaker interference.png

Diffraction - Diffraction is the phenomenon where waves spread around an object. It is partly diffraction in play when you hear sound despite being behind a wall, doorway, or other obstacle—the sound spreads out from an opening to diffract around the object, moving radially away from any boundaries.

Diffraction may be considered as a consequence or a special case of interference. Obstacles that block part but not all of a sound wave essentially convert the unabsorbed sound into one or more point source of sources of sound, which seem to emit sound waves radially and perhaps interfere with each other. Compare, for example, the diffraction of sound waves through two small slits with the interference of sound from two loudspeakers as shown earlier.

Double slit diffraction.png

For those with experience in optics, this is an analogy of the Huygens-Fresnel principle for sound. It also explains why smaller openings result in sound waves spreading out over a wider angle. (Larger openings essentially act as many thin slits separated by infinitely small distance, while smaller openings act as fewer slits, also separated by zero distance.) Of this, Richard Feynman writes that

No-one has ever been able to define the difference between interference and diffraction satisfactorily. It is just a question of usage, and there is no specific, important physical difference between them. The best we can do is, roughly speaking, is to say that when there are only a few sources, say two, interfering, then the result is usually called interference, but if there is a large number of them [possibly infinite], it seems that the word diffraction is more often used.

Dispersion - In many media which we are accustomed to, sound only travels at one speed. This does not have to be the case, however. When waves of different frequencies travel at different speeds, this is called dispersion. Air is non-dispersive, but water and ice do cause dispersion of waves.

Doppler Effect - The Doppler effect occurs when a source of sound or an observer are moving relative to the sound. When this occurs, an observer may count a frequency different from the frequency emitted by the source of sound. A moving source, like the sirens of an ambulance, will inevitable get closer to some previously emitted wavelets and farther from others, leading to some waves bunching up and others spacing out. Observers will also "run into" wavelets of sound at a different rate if they are running towards or against the waves, and this too affects the frequency they measure. The frequency of a Doppler shift of sound is

[math] \frac{f_\text{obs}}{f_\text{src}} = \frac{v + v_\text{obs}}{v + v_\text{src}} [/math]

where [math]v[/math] is the speed of sound, and the positive direction of [math]v_\text{src}[/math] and [math]v_\text{obs}[/math] is from the observer to the source. Unlike many phenomena of sound, the Doppler shift equation for sound is not true of all other types of waves.

Reflection - Reflection occurs when a wave encounters a boundary and as a result moves in the opposite direction. Reflection is responsible for both echoes and reverberation.

A common mistake made by students is to assume that only solid obstacles can cause reflection. While walls and other non-absorbent obstacles may be familiar to most of our everyday experiences, sound waves can reflect off of many sorts of boundaries. For example, it is possible for sound to travel into the upper atmosphere before reflecting back down to the ground.

Refraction - Refraction is the change in the direction of a sound when the speed of sound changes. Different media vary in their speed of sound, leading to refraction as sound enters from one material to another.

Resonance - An object or air column may vibrate at its fundamental frequency or an overtone when a force is applied to the object at certain frequencies. When the force is applied at other frequencies, the object or air does not vibrate with as much energy. In most cases, This phenomenon is called resonance.

The Tacoma Narrows Bridge, located in the state of Washington, collapsed under conditions of high wind in 1940. While teachers and textbooks sometimes attribute the catastrophe to the bridge vibrating in step with the wind, thereby driving resonance, resonance most likely was not mainly responsible for the destruction of the bridge. Newer textbooks tend to identify this report as a misconception or at least contentious.

Past Rules

In 2019, Sounds of Music underwent significant event changes. The following section details the event structure under the old rules, for reference and in the event that the old structure returns in the future.

Past Rules

The Competition

While much of the work for the Sounds of Music event takes place before the competition, in the form of building, tuning, and practicing, only one part actually counts for Science Olympiad, and that is the competition.

The Setup

When you arrive in the competition room, you will be at least 30 seconds, if not more, to set up. If you are ready in less than 30 seconds, you will receive a 5 point bonus. This normally isn't a problem, as most instruments are mounted or otherwise ready to play. Some teams do bring xylophones that are not mounted or otherwise connected, and these teams will likely use the majority of the time. The room will likely have very few resources. There will be music stands where you may place your music, but other than that there is not much you can count on. Some competitions may provide a table or desks to place xylophones on, but it may be smart to bring your own portable table just in case.

During the setup time, introduce yourself to your judges. Provide information such as your name, your school name, the type of instruments you created, and the pieces you will be playing. Give the judges a score of the music you wrote at this time as well.

The Music

The required piece of music this year is the theme from the 2nd movement of Dvorak's New World Symphony. The basic melody, written in the key of C in treble clef, can found on the second page of the Sounds of Music rule sheet. You may alter this piece by transposing it to a key to fit your instrument but the instrument which plays the melody must play the same notes as provided on the rules, with no changes. You will also be expected to compose your own harmony to this piece, which the second instrument will play.

The second piece of music is completely your own creation. You may play anything you wish, from classical to pop to simple tunes like Twinkle, Twinkle, Little Star. It is best to play a song the judge will recognize. As with the required piece, you will need to write out your music with melody and harmony.

Concerning writing the music, there are a few requirements you must abide by. As mentioned before, the melody of the New World Symphony theme must be exactly what is written on the rules (though it may be in a different key). The music the higher instrument plays MUST be written in treble clef, and the music the lower instrument plays MUST be written in bass clef. Give the judges a copy of the music with both parts on the same page- you'll probably get it back later. Also make sure that your names, team name, and team number are on the music, since this is worth a couple points.

It is a good idea to write the music with music notation software. It looks more professional and has been recommended by judges at several competitions. Music software also makes sheet music easier to read, rather than what you may write by hand, no matter how good your handwriting is.

Some suggestions for music notation software are:

  • Forte Notation- Free and paid with 30-day trial
  • MuseScore- Free: MuseScore 2 is easy to use, and work has begun on MuseScore 3
  • Finale- Paid, but has a 30-day trial
  • Sibelius- Paid, very popular

Technical Interview

The final portion of the event is the technical interview. It may be oral or written. In this section, you will have to explain how you built your instruments and how they work. You will also need to explain the sound theory behind your instrument and some of the physics of sound. BOTH team members will need to participate in the interview to get full marks.

The technical interview generally becomes more important as the year goes on (and the competition becomes tougher). This is because your opposition usually gets tougher as well and many more instruments sound 'real'. Because of this, the interview will become a huge separator of teams. Make sure you understand the physics of sound and wave theory, basics of resonance, basics of tempering, and go into as much depth as possible into how your own instruments function. Many people take this part of the competition lightly, but 30 points is nothing to scoff at.

This website provides much of the knowledge needed for the technical interview portion.

Rubric Overview

The highest score possible for this event, according to the rules, is 100. 20 points are awarded for the building and choice of instruments, as well as tuning, 20 points are awarded for being able to play the required scale, as well as sound quality, 20 points are awarded for the performance, 20 points are awarded for the technical interview, and 20 points are awarded for correct music notation, playing in the correct range, and being ready to be judged within 30 seconds of walking into the room.

Previous National Tournament Winners

Team Bass Instrument Treble Instrument
2007 Troy High School Guitar Trumpet
2008 Valparaiso High School Guitar Xylophone
2011 Harriton High School Marimba Flute
2012 Camas High School Marimba Violin

As of 2018-2019 season, there is only one instrument in this event.

Instrument Instructions

Here are websites with tutorials to make instruments:

  • Woodwinds
  • Strings
  • Brass