Which Decepticon transforms into a cassette player?

Soundwave is the Decepticon who transforms into a cassette player.

In the original Generation 1 continuity, Soundwave’s alternate mode is a microcassette recorder or cassette deck. That disguise fits his role as the Decepticons’ communications officer: he can monitor, detect, and jam transmissions while appearing to be an ordinary electronic device. His distinctive chest compartment opens in robot mode and stores cassette-sized spy robots.

Those deployable minions are among Soundwave’s most recognizable features. Ravage, Laserbeak, Buzzsaw, Rumble, Frenzy, and Ratbat are all associated with his cassette mechanism, though the exact roster varies by continuity. The original toy entered Hasbro’s Transformers line in 1984 after originating in Takara’s Micro Change toy range.

Readers sometimes answer Blaster because he is the corresponding Autobot communications character and also uses cassette partners. The distinction is factional: Soundwave is the Decepticon, while Blaster is the Autobot. In later stories Soundwave has received vehicle, satellite, and other alternate modes, but the cassette-player form remains his signature version.