Add comments to wavetable synth examples

examples/Synthesis/Wavetable/MidiSynth/MidiSynth.ino

+/* Play notes when your computer sends USB MIDI messages.
+
+   To use this example, you must run software on your computer which
+   sends MIDI.  Tools > USB Type must be set to MIDI when uploading.
+
+   Requires Teensy 3.6 due to 520 kbytes of wavetable data
+   Requires Audio Shield: https://www.pjrc.com/store/teensy3_audio.html
+*/
+
+// TODO: smaller samples, to fit in Teensy 3.2 memory
 #include "Pizzicato_samples.h"
 #include "FrenchHorns_samples.h"
 #include "Viola_samples.h"

examples/Synthesis/Wavetable/MidiSynthKeyboard/MidiSynthKeyboard.ino

+/* Play notes with a regular USB MIDI Instrument.
+
+   To use this example, connect a USB instrument to Teensy 3.6's
+   USB host port.  This cable is recommended:
+     https://www.pjrc.com/store/cable_usb_host_t36.html
+
+   Requires Teensy 3.6 for USB host capability.
+   Requires Audio Shield: https://www.pjrc.com/store/teensy3_audio.html
+*/
+
+
 #include "Pizzicato_samples.h"
 #include "FrenchHorns_samples.h"
 #include "Viola_samples.h"

examples/Synthesis/Wavetable/GeneralMidiSynth/GeneralMidiSynth.ino → examples/Synthesis/Wavetable/MidiSynthLarge/MidiSynthLarge.ino

+/* Play notes when your computer sends USB MIDI messages.
+
+   To use this example, you must run software on your computer which
+   sends MIDI.  Tools > USB Type must be set to MIDI when uploading.
+
+   Requires Teensy 3.6 due to 820 kbytes of wavetable data
+   Requires Audio Shield: https://www.pjrc.com/store/teensy3_audio.html
+*/
+
 #include "bassoon_samples.h"
 #include "clarinet_samples.h"
 #include "distortiongt_samples.h"

examples/Synthesis/Wavetable/SimpleWavetable/SimpleWavetable.ino

+/* Play a flute sound when a button is pressed.
+
+   Connect a pushbutton to pin 1 and pots to pins A2 & A3.
+   The audio tutorial kit is the intended hardware:
+     https://www.pjrc.com/store/audio_tutorial_kit.html
+
+   Without pots connected, this program will play a very
+   strange sound due to rapid random fluctuation of the
+   pitch and volume!
+
+   Requires Teensy 3.2 or higher.
+   Requires Audio Shield: https://www.pjrc.com/store/teensy3_audio.html
+*/
+
 #include <Bounce.h>
 #include <Audio.h>
 #include <Wire.h>

examples/Synthesis/Wavetable/ZeldaSynth/ZeldaSynth.ino

+/* Play Zelda music.
+
+   Requires Teensy 3.6 due to 520 kbytes of wavetable data
+   Requires Audio Shield: https://www.pjrc.com/store/teensy3_audio.html
+*/
+
 #include <Bounce.h>
 #include <Audio.h>
 #include <Wire.h>

synth_wavetable.h

 #define NOTE(N) (440.0 * pow(2.0, (N - 69) / 12.0))
 #define DECIBEL_SHIFT(dB) (pow(10.0, dB/20.0))
 
+// TODO: move all this stuff into the AudioSynthWavetable class, not global scope
 struct sample_data {
 	// SAMPLE VALUES
 	const int16_t* sample;
 	void playFrequency(float freq, int amp = DEFAULT_AMPLITUDE);
 	void playNote(int note, int amp = DEFAULT_AMPLITUDE);
 	bool isPlaying(void) { return env_state != STATE_IDLE; }
-    void setFrequency(float freq);
+	void setFrequency(float freq);
 	virtual void update(void);
 	
 	envelopeStateEnum getEnvState(void) { return env_state; }