4-step-sequencer

#include "Volume3.h"

#define speakerPin 9

void setup() {
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);

}
int n = -1, last = 0;
void loop() {
  uint16_t volume = 1023;

  int zz = ++n % 4 + 2;
  digitalWrite(zz, HIGH);

  uint16_t frequency = analogRead(zz) & (B11111 << 5);
  uint16_t st = (1023 - analogRead(1)) / 8 + 1;
  uint16_t pwm = (analogRead(0)& (B111111 << 4))+1;

  int freq = frequency > last ? last : frequency;
  int inc = (freq - last) / 8 / ((pwm * st) / 16);
  for ( int i = 0; i < (pwm * st) / 16 ; i++)
  {
    vol.tone(speakerPin, freq / 2 , volume);
    delay(1);
    if ( freq < frequency )
    {
      freq += inc + 2;
      if ( freq > frequency ) freq = frequency;
    }
  }

  vol.noTone();
  delay(((1023 - pwm)*st) / 16);
  digitalWrite(zz, LOW);
  last = frequency;
}