Hello! 
I'm very new to this Arduino community. Recently I am working on a project using a Sharp GP2Y0A21YK0F IR sensor and an Arduino nano to trigger midi message. What I am trying to do is to use the midi message generated by the distance proximity form IR sensor to control the virtual faders and knobs on the DAW. I use Cubase primarily. So basically the IR sensor is like a fader or knob on a traditional midi controller, and I want to map it to a setting of a virtual instrument or effect, such as "master volume", "wet", "resonance", etc... I am not looking for triggering a note-on message or something like that. I guess the Arduino should be output a continuous message. I am using this controller to do simple thing, for example, play a track on Cubase and control the track volume with the sensor. I wonder where should I start with the code? I'm more likely a musician rather than a programmer, so any advice or help would be greatly appreciated, thanks!
Assuming you already have an Arduino and the IR distance sensor, plug it into an analog input and run the [u]Analog Read Serial Example[/u] to see if you're getting meaning/useful readings. (You're not going to read the distance in any meaningful units but you should get bigger/smaller numbers related to the distance.)
...Later on, there is a [u]map()[/u] function if you want to convert those numbers to useful MIDI values.
Then, there a couple of MIDI libraries for USB MIDI or regular serial MIDI. Try sending some MIDI messages under pure-software control with no user-input.
Once you can read the sensor and write MIDI messages, you can write some code tying those together.
I guess the Arduino should be output a continuous message.
You probably only need to send the changes.