Micro Change included the cassette-player Transformers such as Soundwave. Takara introduced Micro Change in Japan in 1983 as a branch of its New Microman line, built around ordinary objects that transformed into robots or other forms.
The concept was deliberately playful: a cassette player, camera, microscope, gun, or watch could become a futuristic robot or accessory. The Micro Change Cassette Man toy was adapted into Soundwave for Hasbro’s 1984 Transformers line. Its cassette companions also drew from the same family of transforming object toys, helping establish Soundwave’s distinctive communications-and-surveillance theme.
Hasbro licensed Micro Change alongside Diaclone and merged selected toys into Transformers. Diaclone mainly supplied vehicle-based robots, which is why it is the answer to the neighbouring question about original car Autobots. Gobots and Machine Robo are separate toy properties and were not the Japanese source line for Soundwave. A related detail often missed is that the original Micro Change toy was not initially marketed as a Decepticon; its Transformers identity and fiction came later.