system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do wind instruments work?

Why do some combinations of holes/valves produce notes and others produce nothing? Why do some need reeds and others work with just air?
gpt
Sound is produced from oscillation (moving back and forth). To create a sound from blowing, you need to cause some part of the instrument to oscillate. Blowing over or between a reed will cause it to vibrate up and down, blowing into a brass instrument's mouthpiece produces vibrations from your lips, and in a flute, blowing over/at the edge affects the pressure within causing vibration.  

For different notes, it's the one time the size of your instrument matters. Sounds propagate and reinforce more in a space the size of their wavelength. A certain length of tube will amplify a certain pitch. Lower pitch notes have a longer wavelength, and are more easily produced by bigger tubes. By closing or opening more holes on an instrument you're manipulating the size of the tube, and as a result, which frequencies get amplified.