basic code for using - updates later

/*
MIDI note player

This sketch shows how to use the serial transmit pin (pin 1) to send MIDI note data.
If this circuit is connected to a MIDI synth, it will play the notes
F#-0 (0x1E) to F#-5 (0x5A) in sequence.

The circuit:
– digital in 1 connected to MIDI jack pin 5
– MIDI jack pin 2 connected to ground
– MIDI jack pin 4 connected to +5V through 220 ohm resistor
– Attach a MIDI cable to the jack, then to a MIDI synth, and play music.

created 13 Jun 2006
modified 13 Aug 2012
by Tom Igoe

This example code is in the public domain.

http://www.arduino.cc/en/Tutorial/Midi
*/
const int ledPin = 13;
const int knockSensor0 = A0;
const int knockSensor1 = A1;
const int threshold0 = 1000;
const int threshold1 = 500;
const int knockSensor2 = A2;
const int knockSensor3 = A3;
const int threshold2 = 1000;
const int threshold3 = 500;

int sensorReading0 = 0;
int sensorReading1 = 1;
int sensorReading2 = 2;
int sensorReading3 = 3;// variable to store the value read from the sensor pin
int ledState = LOW;

void setup() {
// Set MIDI baud rate:
pinMode(ledPin, OUTPUT); // declare the ledPin as as OUTPUT
Serial.begin(9600);
}

void loop() {

sensorReading0 = analogRead(knockSensor0);
sensorReading1 = analogRead(knockSensor1);
sensorReading2 = analogRead(knockSensor2);
sensorReading3 = analogRead(knockSensor3);
// if the sensor reading is greater than the threshold:

if (sensorReading0 >= threshold0)
{

// play notes from F#-0 (0x1E) to F#-5 (0x5A):
// for (int note = 0x1E; note < 0x5A; note ++) {
//Note on channel 1 (0x90), some note value (note), middle velocity (0x45):
// noteOn(0x90, note, 0x45);
delay(80);
//Note on channel 1 (0x90), some note value (note), silent velocity (0x00):
// noteOn(0x90, note, 0x00);
Serial.println(“Knock0!”);
// }
}
if (sensorReading1 >= threshold1)
{
delay(80);
Serial.println(“Knock1!”);
}
if (sensorReading2 >= threshold2)
{
delay(80);
Serial.println(“Knock2!”);
}
if (sensorReading3 >= threshold3)
{
delay(80);
Serial.println(“Knock3!”);
}
}

// plays a MIDI note. Doesn’t check to see that cmd is greater than 127, or that
// data values are less than 127:
void noteOn(int cmd, int pitch, int velocity) {
Serial.write(cmd);
Serial.write(pitch);
Serial.write(velocity);
}