Sound is vibration. All sounds you hear are only movements in the air. A piano string, a person's voice, a storm—all are different patterns of vibration. An analog synthesizer is a machine that makes these vibrations, but using electricity. It creates electrical signals that move in the same way air moves for sound. Then, your speaker turns these electrical vibrations back into sound you can hear. So, if you can control the electrical vibration, you can create any sound you imagine.
The Heart: The Oscillator
The oscillator is where the sound begins. Its job is to make a repeating electrical pattern, which we call a waveform. Change the voltage to the oscillator, and you change the speed of the vibration, which changes the musical pitch.
Inside, an oscillator uses simple parts. A capacitor fills with electricity and then empties, over and over. This filling and emptying makes the wave shape. Different shapes—smooth sine, jagged sawtooth, or a square wave—give you different tone colors. A smooth wave sounds soft, like a flute. A jagged wave sounds bright and rich, like a string section. By mixing these basic shapes, you can build the start of many sounds.
The Sculptor: The Filter
A filter changes the color of the sound. In the real world, sounds are not flat; they have bright and dark parts. A filter works like a sophisticated tone control, cutting away some frequencies and letting others pass.
A low-pass filter removes the high, bright sounds, making everything feel warmer and darker. A high-pass filter does the opposite, removing the low end to make a sound thin and sharp. Many filters can also resonate, which means they boost a narrow band of frequencies. This can make a sound feel like it is ringing, similar to the resonance in a physical object.
The Movement: Modulation
A sound that does not change is a boring sound. Real sounds in nature are always moving. This is where modulation comes in. You use changing electrical signals to control other parts of the synth.
An LFO, or Low-Frequency Oscillator, is too slow to hear. But you can use its slow wave to control something else. If it controls the pitch, you get vibrato. If it controls the filter, you get a sweeping, wah-wah effect.
An Envelope is another kind of controller. It shapes how a sound behaves after you press a key. It defines the attack—how fast the sound starts—the decay, how long it sustains, and the release, how it fades away. This is what makes a plucked string different from a held organ note. You can connect these control signals to almost any part of the synth, creating complex, living sounds.
The Texture: Noise and Extra Effects
To make sounds like wind or percussion, you need randomness. A noise generator produces a messy, unpitched signal full of all frequencies. This is essential for creating natural textures.
You can also create more complex behavior using feedback. This means sending a signal back into its own path. This can create distortion, strange resonances, or metallic tones. Techniques like ring modulation combine two signals to make new, clanging sounds, perfect for bells or special effects.
The Big Picture: Why You Can Make Any Sound
So, with these tools, you have everything. You have the basic sound source (the oscillator). You have a way to shape its color (the filter). You have ways to make it move and breathe (modulation). And you have ways to add randomness and complexity (noise and feedback).
This is the power of your synthesizer. Every sound in the world is just a specific recipe of vibrations. Because you can control every part of the electrical vibration inside your synth, you have the power to cook up any recipe you can think of. From a human voice to a spaceship, it all starts with a simple vibration.
