framework-arduinoteensy-cxx20/libraries/Audio/examples/Synthesis/Guitar/Guitar.ino

#include <Audio.h>
#include <Wire.h>
#include <SD.h>
#include <SPI.h>
#include <SerialFlash.h>

#include "chords.h"

// Special thanks to Matthew Rahtz - http://amid.fish/karplus-strong/

AudioSynthKarplusStrong  string1;
AudioSynthKarplusStrong  string2;
AudioSynthKarplusStrong  string3;
AudioSynthKarplusStrong  string4;
AudioSynthKarplusStrong  string5;
AudioSynthKarplusStrong  string6;
AudioMixer4              mixer1;
AudioMixer4              mixer2;
AudioOutputI2S           i2s1;
AudioConnection          patchCord1(string1, 0, mixer1, 0);
AudioConnection          patchCord2(string2, 0, mixer1, 1);
AudioConnection          patchCord3(string3, 0, mixer1, 2);
AudioConnection          patchCord4(string4, 0, mixer1, 3);
AudioConnection          patchCord5(mixer1, 0, mixer2, 0);
AudioConnection          patchCord6(string5, 0, mixer2, 1);
AudioConnection          patchCord7(string6, 0, mixer2, 2);
AudioConnection          patchCord8(mixer2, 0, i2s1, 0);
AudioConnection          patchCord9(mixer2, 0, i2s1, 1);
AudioControlSGTL5000     sgtl5000_1;

const int finger_delay = 5;
const int hand_delay = 220;

int chordnum=0;

void setup() {
  AudioMemory(15);
  sgtl5000_1.enable();
  sgtl5000_1.volume(0.6);
  mixer1.gain(0, 0.15);
  mixer1.gain(1, 0.15);
  mixer1.gain(2, 0.15);
  mixer1.gain(3, 0.15);
  mixer2.gain(1, 0.15);
  mixer2.gain(2, 0.15);
  delay(700);
}

void strum_up(const float *chord, float velocity);
void strum_dn(const float *chord, float velocity);

void loop() {
  const float *chord;

  // each time through the loop, play a different chord
  if (chordnum == 0) {
    chord = Cmajor;
    Serial.println("C major");
    chordnum = 1;
  } else if (chordnum == 1) {
    chord = Gmajor;
    Serial.println("G major");
    chordnum = 2;
  } else if (chordnum == 2) {
    chord = Aminor;
    Serial.println("A minor");
    chordnum = 3;
  } else {
    chord = Eminor;
    Serial.println("E minor");
    chordnum = 0;
  }

  // then strum the 6 string several times
  strum_up(chord, 1.0);
  delay(hand_delay);
  delay(hand_delay);
  strum_up(chord, 1.0);
  delay(hand_delay);
  strum_dn(chord, 0.8);
  delay(hand_delay);
  delay(hand_delay);
  strum_dn(chord, 0.8);
  delay(hand_delay);
  strum_up(chord, 1.0);
  delay(hand_delay);
  strum_dn(chord, 0.8);
  delay(hand_delay);
  strum_up(chord, 1.0);
  delay(hand_delay);
  delay(hand_delay);
  strum_up(chord, 1.0);
  delay(hand_delay);
  strum_dn(chord, 0.7);
  delay(hand_delay);
  delay(hand_delay);
  strum_dn(chord, 0.7);
  delay(hand_delay);
  strum_up(chord, 1.0);
  delay(hand_delay);
  strum_dn(chord, 0.7);
  delay(hand_delay);

  Serial.print("Max CPU Usage = ");
  Serial.print(AudioProcessorUsageMax(), 1);
  Serial.println("%");
}

void strum_up(const float *chord, float velocity)
{
  if (chord[0] > 20.0) string1.noteOn(chord[0], velocity);
  delay(finger_delay);
  if (chord[1] > 20.0) string2.noteOn(chord[1], velocity);
  delay(finger_delay);
  if (chord[2] > 20.0) string3.noteOn(chord[2], velocity);
  delay(finger_delay);
  if (chord[3] > 20.0) string4.noteOn(chord[3], velocity);
  delay(finger_delay);
  if (chord[4] > 20.0) string5.noteOn(chord[4], velocity);
  delay(finger_delay);
  if (chord[5] > 20.0) string6.noteOn(chord[5], velocity);
  delay(finger_delay);
}

void strum_dn(const float *chord, float velocity)
{
  if (chord[5] > 20.0) string1.noteOn(chord[5], velocity);
  delay(finger_delay);
  if (chord[4] > 20.0) string2.noteOn(chord[4], velocity);
  delay(finger_delay);
  if (chord[3] > 20.0) string3.noteOn(chord[3], velocity);
  delay(finger_delay);
  if (chord[2] > 20.0) string4.noteOn(chord[2], velocity);
  delay(finger_delay);
  if (chord[1] > 20.0) string5.noteOn(chord[1], velocity);
  delay(finger_delay);
  if (chord[0] > 20.0) string6.noteOn(chord[0], velocity);
  delay(finger_delay);
}