Notes

int sensorValue;
// variable to calibrate low value
int sensorLow = 1023;
// variable to calibrate high value
int sensorHigh = 0;
// LED pin
const int ledPin = 13;
void setup() {
// Make the LED pin an output and turn it on
pinMode(ledPin, OUTPUT);
digitalWrite(ledPin, HIGH);
// calibrate for the first five seconds after program runs
while (millis() < 5000) {
// save the maximum sensor value
sensorValue = analogRead(A0);
if (sensorValue > sensorHigh) {
sensorHigh = sensorValue;
}
// save the minimum sensor value
if (sensorValue < sensorLow) {
sensorLow = sensorValue;
}
}
//turn the LED off, signaling the end of the calibration
digitalWrite(ledPin, LOW);
}
void loop() {
//read the input from A0 and store it in a variable
sensorValue=analogRead(A0);
// map the sensor values to a wide range of pitches
int pitch=map(sensorValue, sensorLow, sensorHigh, 50, 4000);
// play the tone for 20 ms on pin 8
tone(8, pitch, 20);
// wait for 10ms
delay(10);
}