I use an external power supply ( http://www.radioshack.com/product/index.jsp?productId=2552560 )

Just to be completely clear I am doing everything correctly and it is just code that is the problem = I disconnect the USB and everything else connected to the arduino (so that when I turn on the arduino the bootloader does not listen to the RX pin thinking a program is being loaded on it), plug in the wall-wart and change the jumper on the arduino to external power, put the LED back in pin 13 and ground, press the reset button, let the program load (which it apparently does not completely do as the indicator LED in pin 13 does not turn on as it does when it is plugged into the computer using USB), then plug all the inputs and outputs back on the arduino (put the MIDI input in the RX pin, the MIDI output in the TX pin, plug in the ground and 5V from the arduino to the breadboard I am using for the components for MIDI i/o, plug in LEDs with 220ohm resistors into digital pins and ground).  Then I play a note on the MIDI keyboard and no LEDs light up corresponding to the MIDI note I played.

It all worked perfectly when I had the USB plugged into the arduino rather than an external power supply.  I think something in the code relies on the computer.  I just do not understand what it is.

Thank you for your help!!!

I am fairly new programing the arduino so I would greatly appreciate any help you can give!

I am able to get the code and hardware to work great as posted by kuk on the following popular post = http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1187962258/0 (thank you kuk!).

But I can only get it to work when the arduino is hooked to the computer via the USB cable.  I want to be able to load a program onto the arduino that can take in MIDI data and respond as I please without the arduino hooked to a computer.  For example, I want to hook my MIDI keyboard up to the arduino, play a note, and in turn an LED on one of the digital pins of the arduino lights up (depending on what note I play).

So, can the arduino take in MIDI data and respond without being hooked to a computer?  If so, how is the code written?

Thank you SO much for your help!  I am working on a project that would greatly benefit from this!

I was able to get the code from the original (first) post to work (I got the hardware to work with no problem).  It works wonderfully when I hook up the arduino to the computer via USB.

Do I have to hook the arduino up to the computer via USB for this code to work?

I want to be able to create an arduino project that will take in MIDI via a 5pin DIN and respond by doing something (such as turn on an LED connected to one of the digital pins) - without needing to be hooked to a computer via a USB cable . . . I want it to be self contained running off a battery or external DC power.  What changes do I need to make to the code in order to make this work?  Is is possible?

FYI - I had nothing hooked to the arduino when loading the program and nothing hooked to the arduino as it boot up after unhooking the USB and changing to external power (changing the power selection jumper).  The LED on pin13 never lights up when I change to external power (no USB) - indicating that the program does not work properly when no USB is used.

I'm sure there is a simple answer to this - I am quite new to programing.  I appreciate any help you have as I am working on an installation piece for next Fall.  

Thank you!