"Chi, chi, chi; ha, ha, ha?" Composer Harry Manfredini revealed that the famous refrain is actually, "Ki, ki, ki; ma, ma, ma," or "kill, kill, kill; mom, mom, mom," which is meant to represent the voice of Jason in his mother's head as she embarks on her rampage.
Composer Harry Manfredini has said the famous "Chi, chi, chi; ha, ha, ha" in the film's score is actually "Ki, k,i ki; ma, ma, ma." It is meant to resemble Jason's voice saying "Kill, kill, kill; mom, mom, mom." So if they Composer doesnt know what he writing who else?