Multiple Velocity Sensitive Piezos!

Other Hardware Sensors
7

It plays a note if the analog input is above 'threshold'. Try setting threshold to 1024. If it still produces output then something is horribly wrong. If that stops the output, lower it to 1000. Continue lowering the value until the output can be triggered by hitting the piezo but will not trigger on its own.

You can unroll the loop if you want but it should not have an effect on the output and it will require that many changes be done four times, making it VERY easy to miss a change.

#include <MIDI.h>

const int InputCount = 4;
int piezo[InputCount] = {
  A9, A10, A11, A12};
int note[InputCount] = {
  50, 51, 52, 53};

const int threshold = 50; //anything over fifty means we've hit the piezo

void setup() {
  MIDI.begin(1);
}

void loop() {
  int sensorReading;

  sensorReading = analogRead(piezo[0]);
  if (sensorReading >= threshold) {
    int maxPiezoVal = getMaxVal(piezo[0], sensorReading);
    byte velocity = map(maxPiezoVal, 0, 1023, 0, 127);//velocity between 50 and 127 based on max val from piezo
    MIDI.sendNoteOn(note[0], velocity, 1);
    delay(10);
    MIDI.sendNoteOff(note[0], 0, 1);
    delay(100);
  }

  sensorReading = analogRead(piezo[1]);
  if (sensorReading >= threshold) {
    int maxPiezoVal = getMaxVal(piezo[1], sensorReading);
    byte velocity = map(maxPiezoVal, 0, 1023, 0, 127);//velocity between 50 and 127 based on max val from piezo
    MIDI.sendNoteOn(note[1], velocity, 1);
    delay(10);
    MIDI.sendNoteOff(note[1], 0, 1);
    delay(100);
  }

  sensorReading = analogRead(piezo[2]);
  if (sensorReading >= threshold) {
    int maxPiezoVal = getMaxVal(piezo[2], sensorReading);
    byte velocity = map(maxPiezoVal, 0, 1023, 0, 127);//velocity between 50 and 127 based on max val from piezo
    MIDI.sendNoteOn(note[2], velocity, 1);
    delay(10);
    MIDI.sendNoteOff(note[2], 0, 1);
    delay(100);
  }

  sensorReading = analogRead(piezo[3]);
  if (sensorReading >= threshold) {
    int maxPiezoVal = getMaxVal(piezo[3], sensorReading);
    byte velocity = map(maxPiezoVal, 0, 1023, 0, 127);//velocity between 50 and 127 based on max val from piezo
    MIDI.sendNoteOn(note[3], velocity, 1);
    delay(10);
    MIDI.sendNoteOff(note[3], 0, 1);
    delay(100);
  }
}

int getMaxVal(int pin, int lastVal) {
  int currentVal = analogRead(pin);
  while (currentVal>lastVal){
    lastVal = currentVal;
    currentVal = analogRead(pin);
  }
  return lastVal;
}