An overdrive pedal turns your guitar up so much that the tops of its sound waves get squashed flat. The squashed waves have extra tones in them, which you hear as grit.
Press the footswitch to compare. Red dashes: the ceiling.
The curve shows what the pedal does to every moment of the wave. Quiet parts come out louder. Loud parts hit the ceiling and stop growing.
A squashed wave is no longer one pure tone. It also has tones at 2, 3, 4 and more times the note's pitch. More drive makes them louder.
A soft pick does not reach the ceiling as often, so less of the wave gets squashed. You can play clean and dirty without touching the pedal.
When several notes are squashed together, the pedal also mixes them into new tones. In a power chord the new tones line up with each other. In a full chord some land a few Hz apart and wobble against each other, which sounds rough.
| New tones | Wobbling pairs | |
|---|---|---|
| Power chord (E5) | 5 | 0 |
| Full chord (E major) | 23 | 5 |
Sets how much the guitar is turned up before the ceiling. More drive squashes more of the wave.
Solid: the curve now. Dashed: Drive at zero.
Turns down the highest of the extra tones. Lower sounds darker; higher sounds brighter and fizzier.
Dots: the 220 Hz tone and its extra tones.
Sets how loud the pedal is. Match it to your guitar alone, or set it louder.
For the 220 Hz tone at this pick. The line marks the guitar alone.
Each button sets the knobs and starts playing. Then change one knob and listen to the difference.