Which audio format is used to create chip tunes? midi, mod, tracked audio, or fm synthesis

FM synthesis

Explanation:

A major advance for chip music was the introduction of frequency modulation synthesis (FM synthesis), first commercially released by Yamaha for their digital synthesizers and FM sound chips, which began appearing in arcade machines from the early 1980s. Arcade game composers utilizing FM synthesis at the time included Konami's Miki Higashino (Gradius, Yie-Ar Kung Fu, Teenage Mutant Ninja Turtles) and Sega's Hiroshi Kawaguchi (Space Harrier, Hang-On, Out Run).