Description:

Used a potentiometer to control the periodicity of repetition of a melody. The serial output shows the periodicity

Components:

Potentiometer, Piezo Speaker

Code:

/* Play Melody
 * -----------
 *
 * Program to play melodies stored in an array, it requires to know
 * about timing issues and about how to play tones.
 *
 * The calculation of the tones is made following the mathematical
 * operation:
 *
 *       timeHigh = 1/(2 * toneFrequency) = period / 2
 *
 * where the different tones are described as in the table:
 *
 * note     frequency     period     PW (timeHigh)   
 * c             261 Hz             3830     1915    
 * d             294 Hz             3400     1700    
 * e             329 Hz             3038     1519    
 * f             349 Hz             2864     1432    
 * g             392 Hz             2550     1275    
 * a             440 Hz             2272     1136    
 * b             493 Hz             2028    1014   
 * C            523 Hz            1912     956
 *
 * (cleft) 2005 D. Cuartielles for K3
 */

int ledPin = 13;
int speakerOut = 7;        
int potPin = 0;
int val = 0;     
byte names[] = {'c', 'd', 'e', 'f', 'g', 'a', 'b', 'C'}; 
int tones[] = {1915, 1700, 1519, 1432, 1275, 1136, 1014, 956};
byte melody[] = "2C2b1a2g2f2e2d2c2c2d2e2f2g2a1b2C2C2b2a2g2p8p8p8p";
                 
// count length: 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0
//                                10                  20                  30
int count = 0;
int count2 = 0;
int count3 = 0;
int MAX_COUNT = 24;
int statePin = LOW;

void setup() {
 pinMode(ledPin, OUTPUT);
 pinMode(speakerOut, OUTPUT);
Serial.begin(9600);
}

void loop() {
  val = analogRead(potPin);
  Serial.println(2+val/2);
  digitalWrite(speakerOut, LOW);    
  for (count = 0; count < MAX_COUNT; count++) {
    statePin = !statePin;
    digitalWrite(ledPin, statePin);
    for (count3 = 0; count3 <= (melody[count*2] - 48) * 30; count3++) {
      for (count2=0;count2<8;count2++) {
        if (names[count2] == melody[count*2 + 1]) {      
          digitalWrite(speakerOut,HIGH);
          delayMicroseconds(tones[count2]);
          digitalWrite(speakerOut, LOW);
          delayMicroseconds(tones[count2]);
        }
        if (melody[count*2 + 1] == 'p') {
          // make a pause of a certain size
          digitalWrite(speakerOut, 0);
          delayMicroseconds(2+val/2);
                  
         
      }
       
    }
  }
}
}

Images:

Piezo and Potentiometer Circuit

Output for periodicity