Ch instead of c
 

See verses 1 and 2:
http://genius.com/Pitbull-chi-chi-bon-bon-lyrics
Sometimes c like in fácil is replaced by ch and it sounds a bit like as they mixed a little bit Italian to Latin-Spanish.

Where does this come from or is this just part of the broad definition of freedom artists have when writing songs?

Tetsuo, what you are explaining, usually doesn't happen in Spanish (at least not in Spain), Pitbull simply plays with the language in his song. Probably he's trying to conceal the rogue subject that it has. In fact the word "chi - chi" does not have an "official" meaning in Spanish, but it is widely understood as the specifical body part defining the female gender.
He uses the verb "tocar" probably because it has two possible translations: to play a musical instrument and to touch something. Thus, by adding "chi-chi bom bom" as an onomatopoeia, he can make the phrase to have a totally inocent meaning as to play the drums and cymbals, but also he suggest the people the second rogue possibility at the same time. ;)

Vale, gracias por la explicación.
Okay, thanks for the explaination.