What Is Sound?
Every sound you have ever heard is the same thing: air pressure wiggling back and forth. A speaker cone pushes air forward and pulls it back; your eardrum copies the motion; your brain calls the result sound. Synthesis is simply deciding, on purpose, exactly how that wiggle should move.
Two properties of the wiggle matter more than everything else combined:
- Frequency: how many times per second the wave repeats, measured in hertz (Hz). Faster repetition = higher pitch.
- Amplitude: how far the pressure swings from rest. Bigger swing = louder sound.
Below is the simplest possible sound: a sine wave, one pure frequency with no extra character. Power it on, then drag the knobs (drag up/down, hold Shift for fine control). Watch the scope while you turn Freq: the wave squeezes together as pitch rises. Turn Level and watch the wave grow taller without changing pitch.
Try this: set Freq to 220 Hz, then slowly sweep up to 440 Hz. That doubling is an octave: the most fundamental interval in music. Every octave up is a doubling of frequency, which is why pitch is a logarithmic experience.
Checkpoint
If a tone at 330 Hz jumps to 660 Hz, what happens to the pitch?