Sending multiple channel MIDI over USB

So I've been experimenting with the whole MIDI over USB thing and have been using an accelerometer to control the values. It calculates tilt, converts to a MIDI value scale of 0-127, and finally sends the value over USB. I've also had success with max/mxp reading the values pf the x-axis and sending them to logic pro as a controller.

How would I send not only the x-axis, but the y-axis to control another parameter over USB? This is obviously a misunderstanding in MIDI format, but I could definitely use some help.

int inpin = 2;                                               // choose the input pin (for a pushbutton)
int val = 0;                                                 // variable for reading the pin status
int groundpin = 18;                                          // analog input pin 4
int powerpin = 19;                                           // analog input pin 5
int xpin = 3;                                                // x-axis of the accelerometer
int ypin = 2;                                                // y-axis
int zpin = 1;                                                // z-axis (only on 3-axis models)
double xval;
double yval;
double zval;
double oxpin = 0;                                               // x-axis origin
double oypin = 0;                                               // y-axis origin
double ozpin = 0;                                               // z-axis origin
byte MIDI_channel = 1;
byte cc_number = 127;


void setup()
{
  Serial.begin(9600);
  pinMode(inpin, INPUT);                                     // declare pushbutton as input
  pinMode(groundpin, OUTPUT);
  pinMode(powerpin, OUTPUT);
  digitalWrite(groundpin, LOW); 
  digitalWrite(powerpin, HIGH);
}

void loop()
{
  xval = analogRead(xpin);
  xval = ((xval*.002929)-1.5)/.3;
  xval = asin(xval);
  xval = abs((xval*(180/3.14)));
  xval = xval*1.411;
  midiMsg(channel+0xB0, 10, xval);
}

void midiMsg(byte cmd, byte data1, byte data2) 
{
  digitalWrite(powerpin,HIGH);  // indicate we're sending MIDI data
  Serial.print(cmd, BYTE);
  Serial.print(data1, BYTE);
  Serial.print(data2, BYTE);
  digitalWrite(powerpin,LOW);
}

By the way, I've noticed many people struggling here calculating tilt with the ADXL330. I used the formula:

arcsine(((Vout-Voffset)/Sensitivity))

Vout = your x value * resolution of your A/D converter
resolution of A/D converter = 3/(2^10); 10 being 10-bit
voffset = 1.5V
Sensitivity = .3V

I'm new, but am really excited about the Arduino!

Another way to put this is how do you send continuous command, number, and value over midi. Printing the value seems to work for 1 channel, but what about multiple channels. Am I stuck adding a MIDI DIN? I would rather stick with USB and use Max/Msp.

If:-
midiMsg(channel+0xB0, 10, xval);
sends CC the messages 10 and the x value then:-

midiMsg(channel+0xB0, 12, yval);
sends CC the messages 12 and the y value

The CC is a message group and you simply need to sent the value to a different controller. Then you can have max pick it up just the same. You don't have to use another MIDI channel.

Read the MIDI protocol again.