added polyphony test file

examples/polyphony_test/polyphony_test.ino

@@ -0,0 +1,79 @@
+//Here, I try to find the true potentional of polyphony for the Arduino Teensy.  Arduino Uno is pretty weak at 7 voices, but the Teensy is very powerful at 16+ voices.
+
+//A potentiometer controls the volume, and a button can oscilate the frequencies.(Note: the more note-polyphony, 
+//the lower the volume you need to set each instrument; otherwise the sound will get cracky) :D
+//Find out more here: https://github.com/nathanRamaNoodles/MusicWithoutDelay-LIbrary
+/*
+  MIT License
+
+  Copyright (c) 2018 nathanRamaNoodles
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files (the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be included in all
+  copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+*/
+#define potPin A0
+
+#include <MusicWithoutDelay.h>
+#include <SensorToButton.h>
+SensorToButton btn(2, 50);  //pin, debounce time(ms)
+#define NUM 7   //Num of voices, you may change this to your microcontroller's processor speed, 
+                //but I have the max number of voices listed on my github: https://github.com/nathanRamaNoodles/MusicWithoutDelay-LIbrary
+MusicWithoutDelay instruments[NUM];
+int vol = 90;
+uint16_t INTERVAL = 15;
+bool mode = true;
+int flip = 1;
+void setup() {
+  // put your setup code here, to run once:
+  Serial.begin(9600);
+  //  while(!Serial);  //For USB devices
+  for (byte i = 0; i < NUM; i++) {
+    MusicWithoutDelay *myInstrument = &instruments[i];
+    float freq = myInstrument->getNoteAsFrequency(NOTE_A3 + i * 4);               //Function gives Frequceny using a Formula.  Every other 4 notes is a harmonic major(something like that)
+    Serial.print(freq); Serial.println(" hz");                            //Print Frequency to Serial
+    myInstrument->begin(CHA, SINE, ENVELOPE0, 0).setVolume(vol).setFrequency(freq);  //set up instruments and their frequencies
+  }
+  pinMode(potPin, INPUT);
+}
+uint32_t pMillis;
+void loop() {
+  // put your main code here, to run repeatedly:
+  uint32_t cMillis = millis();
+  btn.read();
+  for (byte i = 0; i < NUM; i++) {
+    MusicWithoutDelay *myInstrument = &instruments[i];
+    myInstrument->update().setVolume(vol);             //update instruments
+  }
+  if (mode) {
+    vol = analogRead(potPin);
+    vol = map(vol, 0, 1023, 0, 127);
+  }
+  else {
+    if (cMillis - pMillis >= INTERVAL) {   //Vibrato
+      vol += flip;
+      if (vol < 80 || vol > 100) {
+        flip *= -1;
+      }
+      pMillis = cMillis;
+    }
+  }
+  if (btn.wasPressed()) {
+    vol = 90;
+    mode = !mode;
+  }
+}