Lighting musical keys [Example 1]

i'm working on musical instrument turn on led based on key in struck. 16 keys on on multiplexer , 16 led on on port expander.
based on 2 project in arduino playground.

i'm trying add statements
noteon  = ledon
noteoff =ledoff

midi_footsteps exact example i'm trying accomplish
this how mike did http://www.thebox.myzen.co.uk/hardware/midi_footsteps_files/footsteps%20software.zip  it's homepage http://www.thebox.myzen.co.uk/hardware/midi_footsteps.html

can implement port expander , led's section of project sketch attached.

the musical instrument part of mod based on yaami-drum found here http://sourceforge.net/projects/yaamidrum/

below parts i've identified has i2c expander , led. constructing statement , placing @ right point in program still little sketchy.

code: [select]

// defines
// i2c registers
#define i2cregisterinput 0
#define i2cregisteroutput 2
#define i2cregisterpolarity 4
#define i2cregisterconfig 6
#define i2cregisterinterrupt 8
#define i2cregisterexpander 10
// i2c device addresses
#define ledaddress   (0x20 | 0x0)     // address of trigger led indicators output
// control switch device bit masks
#define ddrtrigger 0x00000     // data direction register trigger indictor leds

int lastledval;
#include <wire.h>
  lastledval = 0;                       //leds off
// setup i2c devices
  wire.begin();                      // start i2c interface
  // initilise registers
  gpio_write(ledaddress, ddrtrigger, i2cregisterconfig);   // make outputs
  gpio_write(ledaddress, 0, i2cregisterinput);            // turn them off

 int ledval = 0;
 int ledmask = 1;
 for(int i=0; i<16; i++){
   if(currentstate[i] < threshold) ledval |= ledmask;   // add 1 in position of sensors under threshold
    ledmask = ledmask << 1;   // less on leds off
  }
  if(lastledval != ledval) {   // has changed
  ledmask = 1;                     // led on
    for(int i=0; i<16; i++){
      if((ledmask & ledval) != (ledmask & lastledval)){
        if((ledmask & ledval) == 0) {
          // note off
        controlsend(0x80, control[i], 0x00);   // turn off control message
//notone(8);
digitalwrite(ledpin,low);  
          }
        else{
          // note on
          controlsend(0x90, control[i], currentstate[i]>>3);  // turn on control message
//tone(8, notes[i], 20);
digitalwrite (ledpin,high);
          }
      }
      ledmask = ledmask << 1;  // led high
    }
    // update trigger leds
      gpio_writebyteinverse(ledaddress, ledval, i2cregisterinput);   // update leds
  }
  lastledval = ledval;        // record current state of leds , midi notes / messages
  digitalwrite(ledpin,low);
}          

void gpio_write(int address, int data, int reg) {
 //  send output register address
 wire.begintransmission(address);
 wire.send(reg);
 //  connect device , send 2 bytes
 wire.send(0xff & data);  //  low byte
 wire.send(data >> 8);    //  high byte
 wire.endtransmission();
}

void gpio_writebyteinverse(int address, int data, int reg) {
 //  send output register address
 wire.begintransmission(address);
 wire.send(reg);
 //  connect device , send 2 bytes
   wire.send(data >> 8);    //  high byte
   wire.send(0xff & data);  //  low byte
 wire.endtransmission();
}

int gpio_read(int address) {
 int data = 0;
//  send input register address
 wire.begintransmission(address);
 wire.send(i2cregisterinput);
 wire.endtransmission();
 //  connect device , request 2 bytes
// wire.begintransmission(address);
 wire.requestfrom(address, 2);
if (!wire.available()) { } // nothing until data arrives
   data = wire.receive();

if (!wire.available()) { } // nothing until data arrives
   data |= wire.receive() << 8;
 wire.endtransmission();
 return data;
}


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