MIDIEndpointRef localVirtualEndpoint;
result = MIDIDestinationCreate(virtualMidi,
                               (CFSTR("Virtual Destination")),
                               MyMIDIReadProc,
                               _samplerUnit1,
                               &localVirtualEndpoint);

static void MyMIDIReadProc(const MIDIPacketList *pktlist,
                       void *refCon,
                       void *connRefCon) {


AUGraph *player = (AUGraph*) refCon;

MIDIPacket *packet = (MIDIPacket *)pktlist->packet;
for (int i=0; i < pktlist->numPackets; i++) {
    Byte midiStatus = packet->data[0];
    Byte midiCommand = midiStatus >> 4;


    if (midiCommand == 0x09) {
        Byte note = packet->data[1] & 0x7F;
        Byte velocity = packet->data[2] & 0x7F;

        int noteNumber = ((int) note) % 12;
        NSString *noteType;
        switch (noteNumber) {
            case 0:
                noteType = @"C";
                break;
            case 1:
                noteType = @"C#";
                break;
            case 2:
                noteType = @"D";
                break;
            case 3:
                noteType = @"D#";
                break;
            case 4:
                noteType = @"E";
                break;
            case 5:
                noteType = @"F";
                break;
            case 6:
                noteType = @"F#";
                break;
            case 7:
                noteType = @"G";
                break;
            case 8:
                noteType = @"G#";
                break;
            case 9:
                noteType = @"A";
                break;
            case 10:
                noteType = @"Bb";
                break;
            case 11:
                noteType = @"B";
                break;
            default:
                break;
        }

        NSLog(@" noteType= %@  note number %d",noteType,noteNumber);


        OSStatus result = noErr;
        //MARK: Render
      result = MusicDeviceMIDIEvent (player,
                                       midiStatus,
                                       note+7,
                                       velocity,
                                     0);
    }
    packet = MIDIPacketNext(packet);
}

MIDIEndpointRef localVirtualEndpoint;
result = MIDIDestinationCreate(virtualMidi,
                               (CFSTR("Virtual Destination")),
                               MyMIDIReadProc,
                               _processingGraph,
                               &localVirtualEndpoint);