Creating the beeps and sounds that make up R2's language consisted of electronically synthesised and human-generated sounds:
R2-D2's personality was developing like a toddler's, and Burtt decided that, like a baby, the droid should communicate with recognizable but inarticulate emotional sounds. He added modified human-generated squeaks and sounds into the electronic mix, and the final product ended up being roughly fifty percent synthesizer and fifty percent Burtt doing baby-talk.
The emphasis was apparently put on conveying R2's emotions and attitude in a given situation. However, does the end-result follow any structure of a language? That is, could one (in theory) decipher the syntax of what R2 is saying or are his squeaks and beeps effectively random?
Note: This question is of course out-of-universe. Of course what he says makes perfect sense to 3PO in-universe.