bytebeat.ino

int d = 10;
int led = 13;

int t = 0;
unsigned long lastMicros;
unsigned long deltaMicros;
double timeStep;
double timeUntil;

// the setup routine runs once when you press reset:
void setup() {
  timeUntil = timeStep;
  timeStep = (double)1/(double)8;
  lastMicros = micros();
  for (int i = 0; i<8; i++){
    pinMode(i+2, OUTPUT);
  }
  pinMode(A6, INPUT);
  pinMode(A5, INPUT);
  pinMode(11, OUTPUT);
}

int reado = -1;
int sel = 0;
int par = 0;

int beat(int t){
  if (t%256==0){
    sel = map(
      analogRead(A6),
      0, 1023,
      0, 6
    );
    par = analogRead(A5);
  }
  int p;
  switch (sel) {
    case 0:
      p = map(par, 0, 1023, 0, 31); 
      return ((t<<1)^((t<<1)+(t>>7)&t>>12))|t>>(4-(1^7&(t>>p)))|t>>7;
    case 1: 
      p = map(par, 0, 1023, 0, 31); 
      return t*(t>>((t>>11)&p))*(t>>9&1)<<2;
    case 2:
      p = map(par, 0, 1023, 0, 31); 
      return t>>4+!(-t>>13&7)+2*!(t>>17)|t*t*(t>>(t>>12^t>>11)%3+10)/(7+(t>>10&t>>14&3))*!(t&512)<<3+(t>>p&1);
    case 3:
      p = map(par, 0, 1023, 0, 31); 
      return t>>4|t*t*(t>>6&8^8)*(t>>11^t/3>>12)/(7+(t>>10&t>>p&3));
    case 4:
      p = map(par, 0, 1023, 0, 127); 
      return t*t/(t>>12&t>>8&p)<<7;
    case 5:
      p = map(par, 0, 1023, 0, 127);
      return t*(((t>>12)|(t>>8))&(p&(t>>4)));
    default:
      p = map(par, 0, 1023, 0, 127);
      return ((t >> 10) & p) * t;
  }
}

// the loop routine runs over and over again forever:
void loop() {
  deltaMicros = micros()-lastMicros;
  lastMicros = micros();
  timeUntil-=((double)deltaMicros / (double)1000);
  if (timeUntil<=0){
    timeUntil+=timeStep;
    t++;
    digitalWrite(11, (t%1024!=0 ? LOW : HIGH));
    int n = beat(t);
    for (int i = 0; i<8; i++){
      int one = i+2;
      digitalWrite(one, (n%2==0 ? LOW : HIGH));
      n/=2;
    }
  }
}

The R2R DAC isn't too complicated, it just uses a lot of resistors. There's a good schematic of the module that inspired me here: https://www.olegtron.com/olegtron-r2r-1

The exact values of the resistors are kind of irrelevant, it's mostly only important that the legs have double the resistance of the spine. And if you only have one kind of resistor, you can put two in series to get double the resistance too!