Coding or Wiring? Dual Piezo sensor not triggering LED lights
Well, you never call blink, so leds never get a chance to light up.

Also, you are turning down the led at the begining of each loop. That will cause flickring.

And you don't need so many parameters for blink. In fact, what you need is a little function for blinking just one led.

I think this sketch is what your are looking for (but I can't assure it's correct)

/*
  Dual Piezo Bond Auger Sensor; Blinking LED Light Stack Sketch

  -----------------------------------------------------*/

//Piezo 1 Pin (PiezoPin1)
//Piezo 1 connected to A0
int PP1 = 0;
//Piezo 1 Pin (PiezoPin1)
//Piezo 2 connected to A1
int PP2 = 1;

//Sets the threshold for the detected sound to trigger the LED
const int threshold=0.01;

void setup()
{
    Serial.begin(9600);

    for(int i = 4; i&lt;12; i++) {
        pinMode(i, OUTPUT);
        //sets the led pins 2-11 to output
    }
}

void loop()
{
    /* Read the Piezos
      Reads both piezos and outputs the values. Triggers LED lights
      to fire when a peak voltage is exceeded
      Adjust the value based on the peak signal voltage you
      want to trigger the LED lights*/
    int Piezo1ADC = analogRead(PP1); // Read Piezo 1 ADC value
    float Piezo1V = Piezo1ADC / 1023.0 * 5.0; // Convert to voltage
    int Piezo2ADC = analogRead(PP2); // Read Piezo 2 ADC value
    float Piezo2V = Piezo2ADC / 1023.0 * 5.0; // Convert to voltage
    Serial.println(Piezo1V); //Print the voltage from Piezo 1
    Serial.println(Piezo2V); //Print the voltage from Piezo 2

    if(Piezo1V &gt;= threshold||Piezo2V &gt;= threshold)  //toggle status of LED pins linked to PP1
        // Blink the LEDs on for both Piezos
    {
        {
            littleBlink(2);
            littleBlink(3);
            littleBlink(4);
            littleBlink(5);
            littleBlink(6);
            littleBlink(7);
            littleBlink(8);
            littleBlink(9);
            littleBlink(10);
            littleBlink(11);
        }
    }
}

void littleBlink(int pin)
{
    digitalWrite(pin, HIGH);
    delay(10);
    digitalWrite(pin, LOW);
    delay(10);

}