1. Sources of Sound
To produce sound, we have to make air molecules move back and forth; we can do this either with acoustic vibrations in an enclosed space (e.g. wind instruments) or with vibrations of a fixed solid (e.g. string instruments or hitting a metal pipe) that sets the adjacent air molecules into motion.
Example: a wave in a guitar string moves at 160 ms-1 and has length 0.8m. The fundamental frequency is 100 Hz. Therefore the vibrating air molecules create a sound wave of 100 Hz which travels at 345 ms-1.
In wind instruments the acoustic vibrations in an air column are due to a reed that vibrates in response to the air blown through it.
In brass instruments your lips serve as the reed.

2. When a string on an instrument is plucked, vibrations, that is, waves, travel back and forth through the medium being reflected at each fixed end. Certain sized waves can survive on the medium. These certain sized waves will not cancel each other out as they reflect back upon themselves. These certain sized waves are called the harmonics of the vibration. They are standing waves. That is, they produce patterns which do not move.
On a medium such as a violin string several harmonically related standing wave patterns are possible. The first five of them are illustrated above. It is important to understand that for any one given medium fixed at each end only certain sized waves can stand. We say, therefore, that the medium is tuned.
The first pattern has the longest wavelength and is called the first harmonic. It is also called the fundamental.

3. Depending upon how the string is plucked or bowed, different harmonics can be emphasized. In the animation shown below all harmonics have the same maximum amplitude. This is for purposes of illustration.
Actually, the higher harmonics almost always have maximum amplitudes much less than the fundamental, or first harmonic.
It is the fundamental frequency that determines the note that we hear. It is the upper harmonic structure that determines the timber of the instrument.

4. See Moodle for applet link
Standing Waves, Medium Open At Both Ends, Flute
See Moodle for applet link

5. Musical instruments play different harmonics at the same time
Complex Sound Waves
Musical instruments play different harmonics at the same time f1 f2 f3 =
Shape identifies the instrument

6. Vocal instruments create sound through air passing over the vocal chords causing them to vibrate.  The length and stress on the vocal chords change the pitch of the sounds.  Women generally have shorter, thinner vocal chords than men.  This is the reason for the higher pitch of women's voices.

7. If the same note is played on several musical instruments, the sound is not identical. The waves have the same frequency but different shapes, since other harmonics are also produced by the instrument.

8. Sonic Visualiser Flute notes
Also didgeridoo, clarinet, Amphi zelandica (NZ Cicada)

9. Quality of Sound
A tuning fork produces only the fundamental frequency (1st harmonic).
The same note played on a flute sounds different .The second harmonic is very strong (amplitude) and the fourth harmonic is close in strength to the first.

10. For a clarinet the fifth harmonic is very strong
For a clarinet the fifth harmonic is very strong. The first and fourth harmonics are very similar, with the third being close to them.
In music, the characteristic sound of any instrument is referred to as the quality of sound, or the timbre of the sound.
The quality depends on the mixture of harmonics in the sound.
If the same note is played on several musical instruments, the sound is not identical. The waves have the same frequency but different shapes, since other harmonics are also produced by the instrument.

11. Any periodic wave form can be represented as the sum of sine waves.
Now imagine starting with the complex sound wave, and trying to separate it into sine waves: f1 f2 f3 =
Fourier Analysis
Any periodic wave form can be represented as the sum of sine waves.
Web Link: Fourier series

12. See PhET Fourier
making waves

13. Percussion instrument implies a musical instrument that is played by being hit.
Percussion instruments are basically all about vibration and resonance. In a drum set for example, there is a cylinder which is the body of the drum with a piece of taut material at the top known as the drum head. There may also be another head at the bottom of the drum. When you strike the drum, the head deforms, but the tension causes it to snap back into place, vibrating the air inside the drum. The body of the drum also begins to resonate, as well as the head on the bottom of the drum if it is there, causing a loud sound to come from the drum.